Candidate Supply Is Not a Barrier to Immigrant Representation: A CaseControl Study

Immigrants are underrepresented in most democratic parliaments. To explain the immigrant–native representation gap, existing research emphasizes party gatekeepers and structural conditions. But a more complete account must consider the possibility that the representation gap begins at the supply stage. Are immigrants simply less interested in elected office? To test this explanation, we carried out an innovative case–control survey in Sweden. We surveyed elected politicians, candidates for local office, and residents who have not run; stratified these samples by immigrant status; and linked all respondents to local political opportunity structures. We find that differences in political ambition, interest, and efficacy do not help explain immigrants’ underrepresentation. Instead, the major hurdles lie in securing a candidate nomination and being placed on an electable list position. We conclude that there is a sufficient supply of potential immigrant candidates, but immigrants’ ambition is thwarted by political elites. Verification Materials: The materials required to verify the computational reproducibility of the results, procedures, and analyses in this article are available on the American Journal of Political Science Dataverse within the Harvard Dataverse Network, at: https://doi.org/10.7910/DVN/7GPSCA. Across advanced democracies, immigrant populations have been steadily growing. Within the European Union (EU), more than 1 in 10 residents live in a country other than the one in which they were born. In Sweden, this number reaches 1 in 6.1 This demographic rise has not been matched by immigrants’ representation in electoral politics. In many countries, immigrants remain significantly underrepresented in parliaments (Bird, Saalfeld, and Wüst 2011; Ruedin 2013). To proponents of descriptive representation, this exclusion raises serious questions about the quality of democracy. The absence of descriptive representatives, they argue, marginalizes minority views, whereas their presence enriches parliamentary deliberation. Descriptive representation can also have symbolic value, especially in contexts where minority groups have been historically disadvantaged (Mansbridge 1999; Phillips 1995). More pragmatically, failure to include immigrant candidates can be electorally costly where immigrant electorates are sizable and where native voters also increasingly value diversity (Dancygier 2017; Maxwell 2012). A leading explanation for immigrants’ underrepresentation highlights the role of party elites. Especially in political systems where aspiring candidates require the blessing of party leaders to mount a successful run for office, these gatekeepers, scholars claim, decisively influence the representation of immigrant-origin candidates. Rafaela Dancygier is Professor, Department of Politics and School of Public and International Affairs, Princeton University, Princeton, NJ 08544 (rdancygi@princeton.edu). Karl-Oskar Lindgren is Associate Professor, Department of Government, Uppsala University, Box 514, 75120 Uppsala, Sweden (karl-oskar.lindgren@statsvet.uu.se). Pär Nyman is Postdoctoral Researcher, Department of Government, Uppsala University, Box 514, 75120 Uppsala, Sweden (par.nyman@statsvet.uu.se). Kåre Vernby is Associate Professor, Department of Political Science, Stockholm University, 106 91 Stockholm, Sweden (kare.vernby@statsvet.su.se). We wish to thank Will Horne, Carsten Jensen, Ann-Kristin Kölln, Nazita Lajevardi, Soetkin Verhaegen, Pär Zetterberg, and Richard Öhrvall; seminar participants at APSA, SWEPSA, and Uppsala University; three anonymous reviewers; and the AJPS editors for helpful comments and suggestions. This research was conducted in Sweden and was approved by the Regional Ethical Review Board in Stockholm on September 8, 2016 (approval number 2016/1420-31/5). The project was financially supported by the Swedish Research Council. Data are based on Eurostat; see https://ec.europa.eu/eurostat/statistics-explained/index.php/People_in_the_EU_-_statistics_on_origin_ of_residents. American Journal of Political Science, Vol. 00, No. 00, xxxx 2020, Pp. 1–16 © 2020 The Authors. American Journal of Political Science published by Wiley Periodicals LLC on behalf of Midwest Political Science Association DOI: 10.1111/ajps.12553 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A cross advanced democracies, immigrant populations have been steadily growing. Within the European Union (EU), more than 1 in 10 residents live in a country other than the one in which they were born. In Sweden, this number reaches 1 in 6. 1 This demographic rise has not been matched by immigrants' representation in electoral politics. In many countries, immigrants remain significantly underrepresented in parliaments (Bird, Saalfeld, and Wüst 2011;Ruedin 2013). To proponents of descriptive representation, this exclusion raises serious questions about the quality of democracy. The absence of descriptive representatives, they argue, marginalizes minority views, whereas their presence enriches parliamentary deliberation. De-scriptive representation can also have symbolic value, especially in contexts where minority groups have been historically disadvantaged (Mansbridge 1999;Phillips 1995). More pragmatically, failure to include immigrant candidates can be electorally costly where immigrant electorates are sizable and where native voters also increasingly value diversity (Dancygier 2017;Maxwell 2012).
A leading explanation for immigrants' underrepresentation highlights the role of party elites. Especially in political systems where aspiring candidates require the blessing of party leaders to mount a successful run for office, these gatekeepers, scholars claim, decisively influence the representation of immigrant-origin candidates.
However, for the gatekeeper explanation to be convincing, one crucial piece of the puzzle has yet to be addressed: immigrants' interest in running for office in the first place. If systematic biases are at play in this early supply stage, existing conclusions about the causes of underrepresentation lying at the nomination or election stage may very well be flawed. 2 There are reasons to believe that supply constraints are especially important among immigrants. Migrants settling in a new country might prioritize their economic and social integration over their political engagement. Many of them also confront unfamiliar political environments and electoral institutions. Indeed, local parties frequently lament that they do not have a sufficiently large pool of aspiring immigrant candidates to choose from (Wide 2015). If supply is in fact the critical constraint, researchers may have been too quick to put the blame on party gatekeepers; immigrants may simply show less interest in becoming politically active and holding elected office.
Can supply-side accounts better explain immigrants' political underrepresentation than those highlighting discriminatory party elites? Existing research (e.g., Dancygier 2014;Ruedin 2013;Trounstine and Valdini 2008) examines aggregate statistics of legislatures or candidate pools and, importantly, establishes the extent of underrepresentation and its connection to party gatekeepers or structural factors. But it cannot speak to the question of supply and to the individual-level characteristics that lead immigrants to enter the political fray in the first place.
Furthermore, most work tends to focus on one stage of the representation process. But to better capture the relative importance of supply and demand, studies need to trace the multiple stages that ultimately lead to election, beginning with an individual's predisposition to even consider running for office, to his or her decision to join and be active in a party, to the likelihood of being nominated and, finally, elected. Studying this process is challenging: First, it involves a targeted sampling of candidates and elected politicians along with a sample of individuals who have never run and an oversample of immigrant respondents. Second, it requires surveying a very large number of individuals. After all, most respondents are not expected to seriously consider a run for office, and even fewer are nominated and win. Third, since structural forces influence representation, it is important to place each stage within the relevant local political context. We overcome these challenges by conducting a unique, registry-linked survey of over 6,300 individuals in Sweden. Our survey advances existing research in two critical ways: First, it measures individual-level factors that have been cited as important determinants of participation in electoral politics-including motivation, political socialization, and political interest-but that remain unobserved in studies of immigrant underrepresentation. Second, because we link respondents to richly detailed population-wide registry data, we are able to employ a case-control study, a design typically used in epidemiology to examine individual-level rare events. In our case, this design stratifies our sample such that it contains both a large number of candidates who have been nominated for and elected to municipal office and a sizable number of immigrants (3,455 candidates and 2,280 immigrants). With this approach, we can draw novel and more robust inferences about the stage in the winnowing process at which minority candidates begin to disappear and how contextual factors intervene in this process.
Our main findings are as follows. First, differences in political engagement or ambition cannot explain the immigrant-native representation gap. Our survey demonstrates that immigrants are no less interested, and frequently show more interest, in political matters than natives. They are also slightly more likely to grow up in environments where politics is discussed. Further, they exhibit only somewhat lower levels of political efficacy and discuss politics as frequently as natives, two other important predictors of becoming a politician. In line with these characteristics, immigrants are no less interested than natives in running for office. In short, insufficient supply of willing and interested immigrant-origin individuals is not the crucial constraint.
At what stage of the process, then, do immigrants get stuck? Our second key finding is that the major hurdles for immigrants lie (1) at the nomination stage and (2) in transitioning from being nominated to being placed on an electable list position. On the whole, our findings challenge supply-side explanations and provide more convincing support for the idea that it is party gatekeepers who undermine immigrants' chances to hold elected office. Immigrants do want to enter electoral politics, but they are thwarted by party elites.
These findings withstand several robustness checks: They hold when we examine immigrants with different national backgrounds, when we only examine the most qualified immigrants, when we take party membership into account, and when we relax assumptions about sequencing (i.e., whether party membership precedes or follows interest in elected office). Moreover, though the supply of candidates is analytically distinct from gatekeeper demand, whether or not immigrants expect to be welcomed by party elites likely influences their interest in running for office (cf., Norris and Lovenduski 1995). Our results hold when we take elite encouragement and anticipated elite discrimination into account.
Our study advances existing literature in several ways. First, to the best of our knowledge, ours is the first survey that systematically probes whether and how a wide range of behavioral and attitudinal characteristics are associated with immigrants' entry into electoral politics. In addition to political activity and ambition, our survey taps supply-side variables such as political interest, efficacy, and networks, allowing us to draw a richer and more nuanced picture than has been feasible to date.
Second, our research builds on Lawless and Fox (2010), who surveyed thousands of individuals in four professions that are overrepresented in politics to establish the roots of the gender gap in officeholding in the United States. Going beyond this pioneering work, our case-control design avoids limiting our analysis to such "springboard professions," an important innovation since pathways into office can differ across groups and may not always be tied to certain professions. 3 The design also helps us assess whether candidates and elected politicians differ in significant ways from individuals who never ran for office, and whether these differences vary across immigrants and natives.
Finally, because we are able to link our survey to registry data, we can embed politicians, candidates, and individuals who have not run into their local political environments. Unlike existing work, we can thus study how structural factors (e.g., related to parties, elections, or electoral systems) intervene in the candidate emergence and in the election process.

Existing Approaches
Broadly speaking, research on the political representation of immigrants highlights three sets of factors: (1) the context or political opportunity structure, (2) the preferences of native voters and party gatekeepers, and (3) the political behavior of immigrants themselves. Studies focusing on contextual factors typically look at the composition of legislatures or candidate pools and test whether they correlate with institutional and electoral variables. For instance, variation in citizenship and integration regimes has been shown to affect immigrantnative representation gaps (e.g. Bird, Saalfeld, and Wüst 2011;Dancygier 2017;Garbaye 2005). Within countries, the demographic composition (Farrer and Zingher 2018), in conjunction with electoral rules (Dancygier 2014;Portmann and Stojanović 2019;Trounstine and Valdini 2008), can also influence the descriptive representation of immigrants. Additionally, increases in the number of available seats can affect the election of immigrants (Dancygier et al. 2015), and they have also been shown to matter with respect to African American representation (Marschall, Ruhil, and Shah 2010), perhaps by giving party leaders more flexibility in balancing the slate.
This balancing mechanism suggests that party leaders with influence over nominations can be critical actors, and research indeed documents that party gatekeepers may place immigrants on less competitive slots or not place them at all (e.g. Dancygier 2014; English 2019; Norris and Lovenduski 1995;Soininen 2011;van der Zwan, Lubbers, and Eisinga 2019). This discriminatory behavior can be a function of anticipated voter prejudice (Fisher et al. 2015;Portmann and Stojanović 2019;Street 2014). But party leaders can harbor reservations against including immigrant candidates irrespective of voter resentment. They may hold prejudicial views themselves or fear that the entry of a new group could erode their power. Alternatively, homophily-rather than willful exclusion-may be at work. If the networks and neighborhoods in which party gatekeepers operate feature few immigrants, these elites may fall back on the more familiar native candidate pool. 4 On the flip side, gatekeepers have also actively supported the recruitment of immigrant candidates, in particular when immigrant electorates are key to their party's electoral success. Studies of immigrants' political organization make this case, but they also note party elites' tokenistic approach to immigrant candidates (Dancygier 2017;Eelbode et al. 2013;Garbaye 2005;Maxwell 2012;Michon and Vermeulen 2013;Sobolewska 2013).
Taken together, these varied approaches support the idea that party leaders do not treat prospective immigrant and native candidates equally, but we do not have a full understanding of the nature of this inequality. In particular, studies have not been able to rule out that immigrants are simply less interested in putting themselves forward. They also do not trace the multiple stages of the candidate emergence process, making it difficult to assess at what juncture immigrants drop out. For instance, though studies that examine whole slates of nominated candidates (vs. legislatures) are very useful in establishing inequalities at the nomination stage (Bueno and Dunning 2017;Farrer and Zingher 2018;Shah 2014Shah , 2015; van der Zwan, Lubbers, and Eisinga 2019), they do not consider the pool of potential candidates from which gatekeepers were able to draw.
This omission is potentially critical, for party elites have made claims that immigrant candidates are simply less likely to run (Norris and Lovenduski 1995;Wide 2015). By implication, to make the case that elite (or voter) discrimination leads to representation gaps, scholars sometimes implicitly assume that immigrant and native candidates are more or less equal, save for their country of birth. Yet, elites who confront greater difficulties in recruiting immigrant rather than native candidates might end up nominating immigrant candidates who have less political experience or motivation to run for office.
In short, even though the election of immigrant candidates is a multi-stage process, scholars have thus far mostly neglected the key first stage of candidate supply. To address this issue, we first have to examine whether immigrants and natives differ in their ability and propensity to run for office. With respect to ability, Dancygier et al. (2015) show that differences in human capital and other sociodemographic characteristics cannot explain immigrant-native representation gaps in Sweden. 5 Though the study demonstrates that observable individual resources do not drive representational inequalities, it cannot rule out possibly significant unmeasured factors such as political interest and ambition. It therefore ultimately leaves unanswered the important question of whether immigrants are as likely as natives to be politically engaged and to have considered running for office, or whether they differ in other, heretofore unobserved factors that make them less viable candidates.
Research on the underrepresentation of women in turn suggests that differences in political interest and ambition-themselves partly a function of gendered societal expectations-are quite consequential (Kage, Rosenbluth, and Tanaka 2019;Lawless and Fox 2010). Do analogous forces stunt immigrants' electoral representation? Like women, immigrants often live in societies in which members of their group are not well represented in leadership positions and where stereotypes about appropriate professional and public roles are widespread (e.g., Maxwell 2017). Moreover, immigrants face additional challenges in that they have to navigate a new country, including an unfamiliar political system. The twin pressures of societal expectations and of integrating into a new environment could substantially reduce immigrants' political engagement and interest in running for office.
Evaluating whether immigrants' interest in politics or desire to run for office is more important in producing representational inequalities than are steps that emerge later in the process is fundamental to establishing the sources of underrepresentation, but it is also quite difficult empirically. We next discuss how our study overcomes this challenge.

The Case-Control Design
We situate our study in Sweden, which in many ways typifies the West European immigration experience (unless noted otherwise, when discussing immigrants we refer to the population that is born outside Sweden): Its immigrant population consists of labor migrants, asylum seekers, and those coming for family reasons, and it hails from developed and developing countries. Immigrants in Sweden experience discrimination in the social and economic spheres (Bengtsson, Iverman, and Hinnerich 2012;Vernby and Dancygier 2019), and even though they have long been able to vote and run in local elections (Vernby 2013), they remain significantly underrepresented in elected office. In 2014, the parity ratio at the municipal level (the share of a group in the legislature divided by its share in the population) was 0.45 for immigrants and 1.11 for natives. 6 We focus on election to municipal office because local councils are often the entry point to a political career. Additionally, the systematic exclusion of certain groups from municipal office is consequential because local councils are crucial in the functioning of the Swedish welfare state. They have independent taxation rights (the average municipal income tax rate in 2014 was 21%) and are important public service providers, employing 18% of the labor force in 2016. 7 Local elections are typically contested by several viable parties that span the ideological spectrum (the effective number of parties in 2018 was 5.6). They operate via a party-list proportional system, and party elites in charge of list placement greatly influence candidates' election prospects (Folke, Persson, and Rickne 2016). This institutional setup-at-large elections, proportional representation, party elites determining candidates and their placement, several ideologically distinct partiescharacterizes many West European countries (the United Kingdom and Ireland are exceptions), and we therefore expect our results to speak to this wider set of cases.
As elsewhere, research on immigrant political representation in Sweden has underscored the role of discriminatory party elites (Dancygier et al. 2015;Soininen 2011). But for research on immigrants' political representation in Sweden-and beyond-to make progress, we ultimately need to hear from immigrants themselves. Specifically, we have to establish why immigrants who have the time and resources to stand for election do not end up running and winning. Is it because they simply lack interest in politics? Do they not consider joining parties and competing for office? Do they feel they lack the qualifications for a political career? And how do these previously unmeasured experiences and perceptions compare to those of natives with similar background characteristics?
Answering these questions proves methodologically difficult; fielding a nationally representative survey would yield too few individuals who have been nominated. We address this problem by drawing on work in the field of epidemiology and conduct a so-called case-_ME0107A/ME0107T01/ and http://www.statistikdatabasen. scb.se/pxweb/en/ssd/START__BE__BE0101__BE0101E/ InrUtrFoddaRegAlKon/. control study (e.g. Keogh and Cox 2014). 8 Case-control designs are useful when the outcome of interest is rare in the population under study. 9 If reliable information on the outcome for all units in the population is available, it can be used to take a random sample of the population where the outcome of interest is present (the "cases") and a random sample of the population where the outcome is absent (the "controls"). In the study of representation, individuals running for office are the "cases" and those not running are the "controls." One can then go on to collect previously unmeasured data on the characteristics of the "cases" and "controls" and, after making appropriate adjustments, analyze their correlation with the outcome of interest.
The case-control approach holds promise for students of political representation, as it provides a more efficient way to collect information on the potential drivers of the rare outcomes of interest, namely, standing for and winning election. However, this strategy relies on having access to population-wide data on who has and has not been nominated/elected, information that is frequently difficult to come by.
We therefore turn to Sweden, where such data are available in government registers, allowing us to sample a large number of "cases" as well as "controls." 10 We then administer surveys to both groups to measure variables unavailable in government registers, such as political socialization, interest, and efficacy, among others. The case-control study helps us pinpoint which attitudes, perceptions, and experiences are relevant for becoming an elected politician.
Another challenge in research on minority representation relates to obtaining a large enough sample of individuals belonging to the relevant group. Without oversampling minority populations, estimates will be statistically underpowered. We therefore use populationwide registry data to stratify both the sample of "cases" and "controls," such that the sample contains a significant number of immigrants. This step is crucial given our goal of examining whether there are any group differences with respect to the attitudes, perceptions, and experiences that potentially matter for seeking office. 11 The sample frame included all individuals who were eligible to vote and run in the 2014 local elections. 12 We used six strata, where each stratum is defined by being nominated in 2014 (yes or no) and background or country of birth (immigrant, Swedish-born with at least one foreign-born parent, and Swedish-born with both parents born in Sweden). 13 The survey was administered by Statistics Sweden and was sent to a simple random sample taken from each stratum. Data collection took place between May and September 2017 and used a combination of web-based and postal surveys. Respondents were contacted via mail, and a first invitation contained login information to a web version of our survey, with the remaining four reminders also containing mail-in postal surveys. The survey was administered in Swedish. 14 We selected 16,000 individuals for participation and received answers from 6,386 individuals, yielding a response rate of 40%. 15 To reduce non-response bias, Statistics Sweden provided us with weights that are recalibrated to minimize the difference between the (weighted) respondents and the entire population in the same stratum with respect to relevant registry data. 16 In SI Table B.2 we compare the distribution of a number of key registry variables measuring income, education, and employment status among our respondents to the 11 Because we are combining a case-control study with stratified sampling, we make certain adjustments in the statistical analyses. The fact that we know the exact distribution of "cases" and "controls" as well as immigrants and natives in the population enables us to weight each observation by the inverse of its sampling probability (so-called design weights). 12 Residents 18 years or older who are not Swedish citizens can vote and run if they are EU (or Icelandic or Norwegian) citizens, or if they have resided in Sweden for 3 or more years. 13 In this article we merge the two groups of Swedish-born into one and focus our analysis on the difference between immigrants and natives. As SI Table D.8 shows, our main conclusions remain unchanged when distinguishing between natives with and without foreign-born parents. corresponding distribution in the population of interest, showing that they are, indeed, close to each other.
Finally, our response rate is somewhat lower than Sweden's largest and most well-known public opinion survey by Society Opinion Media (SOM), which has been fielded annually since 1986, and whose response rate has ranged between 48% and 53% in the past 3 years (Tipple 2018). 17 Anticipating this scenario, we included questions that are also fielded by SOM, which allows us to compare response distributions across surveys. Our analysis shows that the distributions of a number of key variables in our survey (societal trust, ideological orientation, party support, and political interest) closely track those found in the SOM study (see SI Table B.4 and SI Figure B.1).

Surveys and Registry Data
The survey groups items into four sections: (1) political interest and networks, (2) political participation, (3) political attitudes, and (4) background characteristics. Using these items, we constructed indices measuring characteristics that are frequently connected with political participation. Following calls for increased scrutiny of the motivations of migrants and other minorities (e.g. Bloemraad and Schönwälder 2013), we measure various forms of engagement in politics . 18 The resulting indices and their component measures are summarized in Table 1 and motivated below.

Internal and External Political Efficacy.
Research on representational inequalities has rarely examined the role of political efficacy (but see Lawless and Fox [2010] on the importance of "self-perceived qualifications"). Political efficacy refers to individuals' beliefs in their ability to influence the political system. Scholars traditionally distinguish internal from external efficacy (Craig and Maggiotto 1982;Pollock 1983). The former refers to a belief in one's own competence. The latter refers to beliefs in the responsiveness of the political system. While conceptually distinct, both types are strongly related to political participation (Abramson 1983;Verba, Schlozman, and Brady 1995). We use four indicators to construct the index of internal political efficacy and five indicators for the index of external political efficacy.
Political Interest. Citizens who are interested in politics participate more than those who are not (Pattie, Seyd, and Whiteley 2003;Verba, Schlozman, and Brady 1995). Differences in political interest have therefore been put forward as an explanation for variation in political ambition between natives and immigrants (Reny and Shah 2018). We construct an index that combines items measuring interest in politics at various levels (from the local to the global) and also include a measure of general political interest.
Political Discussion Networks. Political discussion networks facilitate the flow of political information and are also strongly related to engagement in politics (Huckfeldt and Sprague 1987;McClurg 2003). Our six-item index measures the extent of such networks, based on the frequency of discussion with various interlocutors, ranging from friends and family to the politically active.
Political Socialization. Finally, we include a measure of political socialization. We ask whether respondents discussed political affairs with their parents when growing up, assuming that such discussions will have a positive effect on later engagement in politics (cf. Lawless and Fox 2010).
All indices are unweighted averages of a set of survey items and rescaled to range from 0 to 1. The scales are reliable by conventional standards: Cronbach's alpha ranged from .80 (discussion networks) to .94 (internal efficacy). 19 We further perform several tests to show that the reliability and construct validity of the political engagement indices are very similar across immigrants and natives, giving us confidence that we can meaningfully compare these supply-side variables across groups (see SI Table A.1 and SI Tables D.10-D.12). We also ask respondents for their party preference, as the probability of officeholding depends in part on the party one seeks to represent. Furthermore, party preference and immigrant status are correlated (immigrants are more likely to support leftist parties).
To measure the importance of individual resources, we follow Dancygier et al. (2015) and include the same set of variables capturing the socioeconomic and demographic background characteristics: Sex (1 for female, 0 otherwise), Age (in years), Age squared, Number of children (under the age of 11), Employment status (1 for employed individuals, 0 for all others), Family income (log of equivalized disposable household income), and Years of education.
Moving to contextual variables, our knowledge of respondents' residential location allows us to control for some of the main political opportunity structures highlighted in the literature (Bird, Saalfeld, and Wüst 2011;Dancygier et al. 2015): Seats-to-voters is the ratio of municipal council seats to the number of voters; 20 Effective number of parties 21 measures the number of parties with seats in the local council; and Disproportionality 22 measures the difference between party vote and seat shares. We also include the partisan composition. Left share 23 and SD share measure the vote shares received by leftist parties and the anti-immigration Sweden Democrats, respectively. To measure the demographic composition of the municipal electorate, we include Native education (average years of education among the native electorate), Immigrant share (share of foreign-born in the electorate), and Ethnic concentration (concentration of the immigrant group within the municipality). 24 20 A high ratio makes nominations for office less competitive, but it could also make supply constraints more pressing. Yet even where the seats-to-voter ratio is high, there is little support for supplyside explanations; see SI Figure D.2. 21 Effective number of parties is defined as ( s 2 i ) −1 , where s i is the seat share of party i. 22 We use the Gallagher index, that is G = .5 (v i − s i ) 2 , where v i and s i indicate votes and seat shares of party i, respectively. 23 Leftist parties refer to the Left Party, the Social Democratic Party, and the Green Party. 24 Concentration is expressed in terms of the Herfindahl index, that is, H = d i 2 , where d i is the share of the immigrant group coming from region i. Ideally, d i would denote the share of individuals coming from a specific country, but for reasons of confidentiality we can only distinguish between 27 different regions of birth.

Main Results
For any factor to explain the immigrant-native representation gap, two conditions, at a minimum, need to hold. First, the factor must be correlated with running for office. Second, it must also differ systematically between immigrants and natives.
Beginning with the first, Table 2 shows that candidates and noncandidates differ in predictable ways across the five indices. In substantive terms, candidates score about one standard deviation higher on political interest (SD= 0.23), external efficacy (SD= 0.25), and discussion networks (SD= 0.22). For internal efficacy, the difference is bigger than one standard deviation (SD= 0.29), and for socialization, the difference is just over half of the standard deviation (SD= 0.19). 25 All these factors can therefore be considered as strong predictors for political candidacies.
But do they help explain why immigrants are less likely to run for elected office than are natives? The bottom panel of Table 2 clearly demonstrates that the group differences in the factors that drive political activity are small and inconsistent. Immigrants are, on average, somewhat more interested in politics, whereas natives score more highly on political efficacy. We observe no meaningful group differences when it comes to socialization or discussion networks.
Turning to political ambition, at least as many immigrants as natives appear to have considered running for office (39 and 37%, respectively; in SI Table D.11, we confirm that this question has similar construct validity across groups). It is possible that these numbers are inflated, or at least that they do not reflect a serious consideration of a run for office among a sizable group of respondents. We therefore also examine a more objective measure-party membership-in the next subsection, and again find few immigrant-native differences.
Summing up, the results in Table 2 do not support the idea that immigrants are underrepresented in public office because they lack the requisite political engagement or motivation. The behavioral measures that we found to be important prerequisites for a career in elected However, for immigrants from significant sending countries, the region code is that of the country (for others, the code identifies a set of neighbouring countries). For the coding scheme, see SI Table  D.13. office do not vary significantly across immigrants and natives. In short, it does not appear that immigrants' political underrepresentation is due to an inadequate supply of motivated and politically engaged potential candidates. If candidate supply is not the problem, at what stage of the process do immigrants get stuck? Figure 1 presents a first cut at this question. It shows the share of immigrants at each step in the process that ultimately leads to election. The leftmost bar simply measures the share of immigrants (17.1%) in the eligible population. In a system with perfect parity, the distribution of migrants and natives at each subsequent step should mirror that in this leftmost bar. However, this is only true of the second step, which shows the share of immigrants among those willing to run (18.0%). Once we move from a willingness to run to actually being nominated, we observe a significant drop-off. Further declines emerge at the final stage of election. Among those nominated and elected, immigrants only make up 9 and 6.7%, respectively, suggesting that the major hurdles for immigrants' political representation lie in becoming nominated and, once nominated, in being placed on an electable list position.
These findings once again indicate that the problem does not lie at the supply stage but in the placement of immigrant candidates. To more fully test the supply-side explanation, we move on to multivariate regression analysis. As a benchmark, we first estimate a bivariate model. We next estimate the full model, which includes the five indices, individual-level resources, and other sociodemographic characteristics (e.g., education, employment, income, sex) that could potentially impact supply. We further control for municipal political opportunity structures, as these could influence immigrant-native gaps at each stage of the process (see the section "Surveys and Registry Data" for the complete list of variables).
If there is an underrepresentation of immigrants at any step, the coefficient for the migrant indicator will be negatively signed in the bivariate model. And if any such underrepresentation can be explained with reference to our supply-side factors, the migrant indicator will be indistinguishable from zero once these factors are controlled for. Table 3 shows that the inclusion of controls can only partly account for the representation gap. Beginning with the results in the first column, which are from the model that uses the entire sample to estimate the probability that immigrants and natives become politicians, the coefficient of the constant in the bivariate model (Panel A) shows that an estimated 0.16% of natives become elected politicians. The corresponding figure for immigrants is 0.10 percentage points lower (see coefficient of the immigrant indicator). Immigrants are thus only 35% as likely to be elected to political office as natives-a substantively important difference. This is the number reported in the last row of Panel A ("transition ratio"). In the full multivariate model (Panel B), the four indices that measure political interest, efficacy, and discussion networks have the expected effects on the probability of being elected. Yet the inclusion of these, and of other controls, can only partly account for the immigrant-native representation gap. In the full model, the coefficient for the migrant indicator is smaller, but still statistically and substantively significant. 26 We next turn to models analyzing the steps toward becoming an elected politician, which are in the remaining columns of Table 3 and are also illustrated in Figure 2. Thirty-five percent of natives are willing to run, whereas the corresponding figure for immigrants is 37.5% (0.35 + .025). Taken at face value, the relative willingness to run for office is thus about 7% higher among immigrants compared to natives, as indicated by the number between the two left boxes at the bottom of Figure 2 (107.3%). This difference is, however, small and not statistically significant (p > .10).
Just as in our previous analyses, the underrepresentation of immigrants does not seem to be due to immigrants being less interested in running for office. Rather, they experience greater difficulties than natives in transitioning from being interested in running to actually getting themselves nominated, and from being nominated to being elected. Whereas 2% of natives go from being willing to run to actually running, the corresponding figure for immigrants is 0.9% (0.02 − .011). This difference is not only statistically significant but it is also substantively large: Natives are more than twice as likely to transition to the nomination stage than are immigrants. Finally, while an estimated 22.4% of nominated natives are elected, the corresponding figure for immigrants is only 16.2%, which is equivalent to a 28% (100 − 72) reduction in the likelihood of transitioning to the last stage of winning elected office.
The multivariate regression models analyzing the steps toward elected office further drive home the point that the small and inconsistent immigrant-native differences in the indices that measure political interest, efficacy, discussion networks, and socialization cannot Note: Entries are OLS regression coefficients except for the transition ratio, which is calculated as the coefficient for the immigrant indicator plus the constant (the transition probability for immigrants) divided by the constant (the transition probability for natives). Results in Panel B include the full set of demographic, socioeconomic, opportunity structure, and party controls; see SI Table D.1 for more detailed results, including those for all controls. Significance tests are based on robust standard errors. † p < .10, * p < .05, * * p < .01. explain immigrant underrepresentation. Even when we take all the control variables into account, the share of immigrants who transition from being willing to run to doing so is still more than 40% lower than that of natives (100 − 56.9 = 43.1%). Likewise, the adjusted proportion of immigrants who transition from the penultimate to the final stage is estimated to be 19.1% (100 − 80.9) lower than the share of natives who do so.
To summarize, the results in this section show that previously unmeasured differences in supply-side variables such as political interest, efficacy, discussion networks, and ambition do not help explain the representation gap. Neither do individual-level resources, demographics, or variables that capture the local political context. Rather, the major hurdles for immigrants lie in translating their political interest and motivation into a nomination for elected office and, once nomination is secured, in being placed on an electable list position. We next turn to assessing the robustness of our results in the face of several potential objections.

Robustness Checks and Extensions
We first examine the potential importance of an intermediate step, becoming a party member. Since Swedish local elections operate by a party-list system, individuals who want to run for office have to first join a party. Indeed, lower levels of party membership have been identified as a factor limiting the supply of immigrant candidates (e.g., da Fonseca 2011). Our analysis could therefore be missing a crucial step: Immigrants could simply be less likely to become party members, and this difference could explain their difficulty in transitioning to the nomination stage. Fortunately, our survey allows us to examine this question directly. Beginning with attitudes, 38% of immigrants answer that they could consider joining a party compared to 42% of natives. Though this is a statistically significant difference (p < .01), it is not sizable enough to explain the representation gap. Moreover, when we examine actual party membership, there are no statistically significant (p > .10) group differences. Among immigrant respondents, 5% report that they are currently party members and 12% that they were ever members. The corresponding figures for natives are 6% and 14%, respectively. Turning to the length of membership, native nominees report having been members for approximately 12 years, whereas the corresponding figure for immigrant nominees is 10 years. This difference is not statistically significant (p > .10).
Despite quite small immigrant-native differences in party membership, we reestimated our model in Table 3,  Table 3. Numbers in boxes are estimated population totals. Numbers above arrows in the first two rows are transition probabilities (expressed in percentage points). Numbers below arrows in the second row are adjusted transition probabilities, capturing what transition probabilities would be for immigrants if they were identical to natives with respect to all control variables used in the analysis. Numbers above arrows in the last row are immigrant transition probabilities as a percentage of native transition probabilities. Numbers below arrows in the last row are adjusted transition probabilities for immigrants as a percentage of native transition probabilities. Significance tests are based on robust standard errors. †p < .10, * p < .05, * * p < .01.

FIGURE 2 Transition Probabilities for Natives and Immigrants
this time adding the step of becoming a party member as an additional robustness check. 27 We also considered the possibility that the sequencing could differ, namely, that party membership precedes interest in elected office (see SI Table D.3 and SI Table  D.4). 28 When we incorporate party membership in these ways, our conclusions remain unchanged: Immigrants are less likely than natives to become nominated and be placed on an electable list position, and this difference cannot be explained with reference to supply-side factors, including party membership. 29 Second, our analyses thus far have examined the entire sample of eligible residents. But could it be that parties "skim off the top" of the pool and select the most promising candidates? If so, the sample we analyze 27 See Erlingsson, Persson, and Öhrvall (2012) for an argument about the importance of including this step in the Swedish case. 28 In our survey, 43% of those running for office first joined a party and later decided to run, whereas 12% became party members because they wanted to become a politician. 45% are unable to say which came first. To better establish connections with existing literature (e.g., Lawless and Fox 2010), we present results that consider interest in running as the first step in the main article. 29 These conclusions also hold in analyses that do not include willingness to run at all, and in which party membership is the only step preceding nomination (see SI Table D.5).
would not be the relevant one when studying who becomes a representative and, by implication, when assessing the immigrant-native representation gap. We have already shown that it is mainly individuals with certain characteristics-those of higher socioeconomic status, political interest, and efficacy-who effectively make up the candidate pool. Does the immigrant penalty disappear once we restrict our sample to this group? To investigate this possibility, we first estimate the predicted probability of being elected and then rerun the model for those scoring in the top x percentiles on election probability. In Figure 3, we plot the coefficient for the migrant indicator when we let x vary from 10 to 100. Rather than disappearing at the top of the distribution, the migrant penalty is actually the most severe here: As we continuously restrict the sample to ever more qualified potential candidates, the negative relationship between being an immigrant and attaining elected office strengthens. Panel (a) illustrates this pattern when examining the share of the population who gets elected. When we disaggregate the election process as well as the sample in the following panels, we once more find that immigrant-native gaps do not emerge with respect to willingness to run for office, but that they appear at the nomination and election stages. In short, our previous findings are not driven by our broader focus on the entire eligible population. For similar reasons, we also rerun our analyses with a more restrictive definition of political ambition, where we only count those who answer "yes, absolutely" as willing to run for office. The results, presented in SI Table  D.9, do not differ much from the main results.
Third, our main analysis does not distinguish between immigrants from different regions of the world. Statistical power considerations prohibit a detailed analysis of "origin effects." However, given the salience of ethnic and racial discrimination both inside (English 2019;Eriksson and Vernby, forthcoming;Portmann and Stojanović 2019) and outside (Bengtsson, Iverman, and Hinnerich 2012;Vernby and Dancygier 2019) the electoral arena, we examine whether our findings about immigrants getting stuck at the nomination and election stages are mainly driven by non-European migrants. Alternatively, it is conceivable that immigrants originating outside Europe are less likely to consider elected office since the political systems of their home countries, which are often nondemocratic, are quite different from the Swedish system. Party elites may therefore face particular supply constraints when it comes to this group. We thus reanalyze our results, each time restricting the immigrant sample to the following regions: Africa, sub-Saharan Africa, the Middle East and North Africa, the Nordic countries, and Europe (excluding Nordic countries). We find that irrespective of of their national origins and associated ethnoracial or religious backgrounds, the share of immigrants in the candidate and politician pool falls below their share in the population, and supply-side variables cannot account for this gap. Similar to other work, we also find that migrants with roots outside Europe are less likely to be elected once nominated, a disadvantage arising from less favorable list placement. Going beyond existing work, we can determine that this disadvantage does not result from lacking political engagement. 30 Finally, up to now we have conceptualized supply and demand as separate processes. But it is also possible that anticipated demand affects supply (Norris and Lovenduski 1995;Shah 2014). Underrepresented minorities may expect discrimination from politicians and voters and therefore do not put themselves forward. 31 To test for this possibility, we measured respondents' expectations about societal and political discrimination as well as elite encouragement. We find that immigrants are less likely to expect that they would feel welcome in politics and more likely to believe that migrants are discriminated against in society. For example, immigrants are about twice as likely as natives to expect not to feel welcome as new members of the local parliament. In addition, a significantly (p < .01) higher number of native politicians stated that they had been encouraged to run by the election committee, by the party board, or by other party members (for more details, see page 13 of Appendix D). Do these expectations influence supply? When we reanalyze our main results (i.e., Table 3) and add controls for both expected societal and political discrimination, as well as indicators of elite encouragement, we find that these variables mostly have the expected effects, but our general conclusions remain unaltered. Comparing the full model in SI Table D.7 to that in our main results section (Table 3), we find that the negative relationship between being an immigrant and attaining elected office is hardly affected at all by the inclusion of perceived discrimination and elite encouragement.

Conclusions
With the steady growth of immigrant populations across democracies, immigrants' political underrepresentation has attracted increasing attention from scholars and parties alike. Existing research has frequently blamed discriminatory party elites or native voters for representational inequalities, but it has paid scant attention to candidate supply. This is a potentially serious omission.
To investigate whether supply significantly constrains immigrant political representation, we innovate 30 In another test, we restrict our sample to respondents born outside of OECD countries and to those who self-identify as Muslim, with similar results; see SI Figure  by introducing a new type of survey design to the study of representation. Our case-control study is unique in that it draws from the entire eligible population to produce a large, nationally representative sample of candidates and noncandidates of both immigrant and native background. It is thus the only study that leverages large-scale individual-level data, links these data to structural conditions, and then assesses whether supply-side factors-such as political interest and motivation-drive underrepresentation.
Using these data, we can show that differences in motivation and political engagement cannot explain the immigrant-native representation gap. Immigrants appear to be no less interested in political matters than are natives. And while their sense of political efficacy is slightly lower, they discuss politics as frequently as do natives, are more likely to have grown up in environments in which politics are discussed, and are consequently no less interested in running for office.
Rather than insufficient supply, we find that the major obstacles for immigrants lie in transitioning from (1) being willing to run for office to actually being nominated and (2) from being nominated to being placed on an electable list position. Moreover, these hurdles remain even when we control for a large number of variables measuring individuals' resources, motivations, and perceptions, as well as the opportunity structures in which they are situated.
On the whole, our findings challenge supply-side explanations and provide more convincing support for the idea that it is party gatekeepers who undermine immigrants' chances to hold elected office. The question that naturally follows is why party elites are reluctant to promote the electoral careers of immigrants. Our findings hold across the ideological partisan spectrum, so it is unlikely that anticipated electoral penalties constitute the major driving force. Future research should therefore distinguish between party gatekeepers who willfully leave immigrant candidates off the ballot from those who fail to nominate these candidates because they do not have much contact with immigrant communities and hence are not sufficiently aware of potential immigrant candidates. In many countries, immigrants and natives do not share the same residential space, and this segregation could have an impact on recruitment. 32 In fact, according to our analysis of registry data, the average Swedish adult lives in a neighborhood whose adult population consists of 18.6% immigrants, but for the average elected politician, this number drops to 13.5%. Additionally, our survey reveals that many more natives than immigrants personally know party activists and elected politicians. 33 If lacking intergroup social contact is an important impediment to immigrant recruitment-and one that is more significant than a feared native backlash-parties that want to increase immigrant representation can invest in organizational structures and outreach efforts. Conversely, if segregation and lacking contacts are symptoms of prejudice and discrimination, these measures would likely fail. That gatekeepers place so many fewer immigrant than native nominees on competitive list positions indicates that lacking knowledge of aspiring immigrant candidates provides a partial answer at best.
Lastly, juxtaposing contact and segregation with presumed electoral penalties could also shed new light on the differing sources of underrepresentation across groups. Women are not residentially segregated from elected politicians and party activists, so it is less plausible that party gatekeepers would not come into contact with qualified potential female candidates, and research has instead pointed to gendered societal expectations in suppressing candidate supply (e.g., Kage, Rosenbluth, and Tanaka 2019;Lawless and Fox 2010). Future work can test whether and how differences in stereotypes and prejudice across groups generate different obstacles on the path toward equal representation.