Populists in Parliament: Comparing Left-Wing and Right-Wing Populism in the Netherlands



In parliament, populist parties express their positions almost every day through voting. There is great diversity among them, for instance between left-wing and right-wing populist parties. This gives rise to the question: is the parliamentary behaviour of populists motivated by their populism or by their position on the left/right spectrum? This article compares the parliamentary voting behaviour of the Dutch SP and PVV, the only left-wing and right-wing populist parties that have been in a Western European parliament for more than four years. We find that for their voting behaviour the left/right position of these populist parties is more important than their shared populism. Only on one core populist issue (opposition to supranational institutions) do we find strong similarity in their voting behaviour.

Since the 1990s the number of populist parties has increased greatly in Western Europe. While the political science literature has focused mainly on the success of radical right-wing populist parties (De Lange, 2008), there has also been a growth of those that are left-wing (Lucardie and Voerman, 2012; March and Mudde, 2005). The main feature that left and right populist parties share is that they separate society into two antagonistic groups, ‘the pure people’ and ‘the corrupt elite’ (Mudde, 2004, p. 543). Populists claim that, contrary to the ruling elites, they will make good on their promises. The question is whether populist rhetoric in election campaigns is indeed consequential for populist parties' behaviour after the elections.

This article examines the behavioural consequences of populism: whether the populist character of parties has any implications for how they act in parliament. Whereas many scholars have examined the rhetoric of populist parties, for instance in their election manifestos or their speeches, the actual behaviour of populist politicians in parliament has not been studied in great detail (Barr, 2009; Canovan, 1981; De Lange, 2007; Jagers and Walgrave, 2007; Mudde, 2007; Rooduijn and Pauwels, 2011; Vossen, 2011). At the same time, there is a growing party politics literature that examines ideology in behavioural terms, usually focusing on the roll-call voting behaviour of members of parliament (Hug and Schulz, 2007; Jun and Hix, 2009; Otjes, 2011; Poole and Rosenthal, 2009). These studies quite consistently find that politicians who share, for instance, a left-wing ideology do not only have a shared rhetoric but also vote in the same way on legislation. We pose the question of whether the same applies to populist parties: to what extent do left-wing and right-wing parties that are characterised as populist behave similarly in parliament?

This article examines the parliamentary behaviour of two populist parties in the Netherlands: the left-wing populist SP and the right-wing populist PVV. This pair of parties presents a unique opportunity, because they are the only left-wing and right-wing populist parties in Western Europe to be in a national parliament at the same time for more than one parliamentary term (Hakhverdian and Koop, 2007). This allows us to compare directly their voting behaviour across a wide range of issues. Even though this article focuses on a single country, it shows that parliamentary (voting) behaviour provides a rich data source that may contribute to the debate on populism.

Populism, the Left and the Right

There is considerable debate on the definition of populism. Generally, it is described with reference to two particular claims (Albertazzi and McDonnell, 2008; Jagers and Walgrave, 2007; Mudde, 2004; 2007; Taggart, 2000). The first claim of populists is that the actions of the government should reflect the general will of the people. The people are considered to be pure and uncorrupted. ‘The people’ does not refer to all citizens of a country but rather an imagined ‘heartland’ of ‘a virtuous and unified population’ (Taggart, 2000, p. 95). Second, populists claim that the current political establishment fails to represent the people. The political elite has corrupted and distorted politics in order to deprive the people of power for the sake of their own. The role of the populist party is to ‘give back the government’ to the people.

A third claim is sometimes added to the definition of populism, namely that there is a group of ‘others’ in society who do not belong to the people (Albertazzi and McDonnell, 2008): in many cases they are migrants, who are foreign to the virtuous culture of the people, but these could also be defined in terms of socio-economic status (for example ‘the 1 per cent’ richest people). The elite is said to cooperate with or defend the interests of this other group instead of defending the interests of the people. We, however, agree with Cas Mudde (2007) and Koen Vossen (2010) that this third claim is not a part of the core of populism. Anti-immigrant views are a characteristic of radical right-wing populism rather than populism per se (Mudde, 2007). The key features of populism are clearly pointed out in the definition of populism put forward by Mudde (2004, p. 543), which we adopt: ‘populism is an ideology that considers society to be ultimately separated into two homogeneous and antagonistic groups, “the pure people” versus “the corrupt elite”, and which argues that politics should be an expression of the volonté générale (general will) of the people’.

Most scholars agree that populism has ‘a chameleonic quality’ (Taggart, 2000): it can be combined with different political positions and be used by politicians with different ideologies. Some describe populism as an ideology with an ‘empty heart’ (Taggart, 2000), and stress its thin or partial nature (Stanley, 2008). The notion of populism as a thin ideology is borrowed from Michael Freeden (1996), who proposes that some ideologies are not comprehensive and can therefore be combined with other political ideologies. Many scholars subscribe to the idea that populism can be attached to other political ideas and positions (Albertazzi and McDonnell, 2008; Jagers and Walgrave, 2007; Lucardie and Voerman, 2012; Mudde, 2004; Stanley, 2008; Taggart, 2000). Populism concerns only the relationship between the people and the elite. Who belongs to the elite or the people depends on the orientation of the populist.

Left-wing populism is characterised by an emphasis on socio-economic issues (March, 2007, p. 74). Left-wing populists often claim that the political elite only look after the interests of the business elite and neglect the interests of the common working man (Mudde, 2007). Examples include Die Linke in Germany, Sinn Féin in Ireland and the Socialist Party in the Netherlands (Hakhverdian and Koop, 2007, p. 408; March, 2011, p. 118). Right-wing populist parties, on the other hand, usually receive their ‘radical right-wing’ label with reference to their commitment to authoritarianism and nativism, which is the idea that only members of its nation should inhabit a state and that non-native elements pose a threat (Mudde, 2007). On socio-economic issues, these parties have varying positions, with some parties sharing a neo-liberal economic agenda (such as List Pim Fortuyn in the Netherlands), while parties of what Sarah De Lange (2007) calls the ‘new radical right’ take a more centrist position on socio-economic issues (e.g. the French Front National in recent years). Thus, the label left-wing populist refers mainly to these parties' positions on socio-economic issues, while right-wing populism is usually related to these parties' stances on authoritarianism and migration.

Most studies of populism have looked at the rhetoric of populist parties, their electoral appeal or their policy positions. This also means that researchers have mainly studied materials that relate to how populist parties operate in the electoral arena or in the media (Jagers and Walgrave, 2007; Rooduijn and Pauwels, 2011). These studies show that left-wing and right-wing populist parties share a ‘populist’ rhetoric that is anti-elitist and that claims to represent ‘the people’. With regard to populist parties' substantive positions, however, different methods, such as manifesto, expert survey and voter survey analyses have resulted in divergent interpretations: some put left-wing and right-wing populists on opposite sides of the political spectrum, while they are positioned quite closely together in other studies (Hawkins, 2009; Keman and Pennings, 2011; Van der Brug and Van Spanje, 2009). One explanation is that manifesto analysis, expert surveys and voter surveys all measure something different: perceptions are not necessarily the same as pre-electoral promises outlined in manifestos. It may be the case that left-wing and right-wing populists share, to a large degree, their electoral rhetoric, but behave differently in the eyes of voters and experts. It is an open question whether populists have to back up their populist rhetoric with populist actions. Do left-wing and right-wing populist parties only share populist rhetoric, or do they also act similarly in parliament when the core claims of populism are in play?

This article examines the behaviour of populist parties in parliament. Parties can discuss all kinds of policies in their election manifestos, but by their parliamentary behaviour parties actually commit themselves to policies: it is easy to say one thing and vote for another (Laver and Shepsle, 1999). Parliamentary voting behaviour provides a rich source of data, which has been studied in many countries (Hug and Schulz, 2007; Jun and Hix, 2009; Otjes, 2011; Spirling and McLean, 2007). Existing studies show that party ideology explains a great deal of the differences in voting behaviour (Hix, 2001), although different factors such as whether a party is in a governing coalition also affect their behaviour (Otjes, 2011).

From the core claims of populism one can derive a number of subjects on which populist parties (left-wing or right-wing) should be in agreement if populism is indeed a thin ideology. First, populists want to return power to the people. Populist democracy consists of three parts according to Mudde (2007, pp. 150–5). The first part is plebiscitary politics: decision-making power belongs to the majority of the people instead of the old elites. To achieve this, populists propose reforms such as referenda, citizens' initiatives and recall of elected representatives (see also Albertazzi and McDonnell, 2008; Lucardie and Voerman, 2012). The second part of populist democracy is the personalisation of power, that is, the direct election and increased power for political executives, without the interference of intermediate bodies. As its third point populist democracy entails the primacy of the political, that is, that legal institutions should not limit the will of the people.

H1: Democratic reform hypothesis. Left-wing and right-wing populist parties will behave more alike on the issue of democratic reform than on other issues.

Second, populists want the unmitigated voice of the people to be heard. They generally oppose transferring decision making to non-majoritarian or supranational institutions, in particular the bureaucracy and European Union (EU). These institutions stop the people from implementing the volonté générale (Mudde, 2004). The European Union is one of the most visible institutions in this respect. Populists distrust the bureaucratic politics of the EU (Taggart, 2004, p. 91). Eurosceptics emphasise the ‘democratic deficit’ in the EU (Taggart, 2004, p. 277): institutions of the European Union do not have the democratic legitimacy that national states have. Euroscepticism has often been anti-elitist because it champions popular demands for more democracy (Taggart, 2004, p. 270). While in the past some populist parties have supported European integration (Mudde, 2007), today most populists in Europe can be classified as Eurosceptic. Left-wing Eurosceptics see the EU as an elitist capitalist project that disfavours the interests of the common working man, while right-wing Eurosceptics see the EU as a challenge to national sovereignty (Taggart, 2004, p. 281). Therefore, we expect populists to oppose the transfer of competences to supranational organisations such as the EU (Hooghe et al., 2002; Kriesi et al., 2008; Mudde, 2010).

H2: European integration hypothesis. Left-wing and right-wing populist parties will behave more alike on the issue of European integration than on other issues.

Parties' behaviour is not only determined by their populist nature, but also by other policy views, such as their left–right position. Left-wing and right-wing populists are therefore not expected to behave exactly the same on issues that relate strongly to the left–right dimension. Parliamentary behaviour seems to be structured even more strongly by left–right and opposition–coalition dynamics than is parties' electoral behaviour (Otjes, 2011). What can be expected, however, is that populists behave more alike on the core issues of populism than on other issues. We do not expect absolute agreement of left-wing and right-wing populists on these issues, but a relatively high level of agreement compared to their voting behaviour on other issues. Furthermore, we would expect that on issues that relate to the core of populism populist parties do not only behave more alike, but also that this would set them apart from other parties, at least to a degree. After all, if populism is a thin ideology that influences behaviour, this implies that non-populist parties are expected to be less inclined to behave that way. If a certain issue is strictly related to populism, we would expect populist parties to vote differently from non-populist parties. In practice, however, there will be non-populist parties that agree with populists on some issues, for example democratic reform (e.g. the introduction of a referendum). Thus the degree to which behaviour on democratic reform and European integration sets populists apart from other parties tells us something about the degree to which issues are exclusively related to populism.

We compare behaviour on issues connected to the core of populism with parliamentary behaviour concerning other issues. In particular, we focus on issues that define the difference between left-wing and right-wing populism. We understand the terms left and right from the perspective of the super-issue, which incorporates most issues (Mair, 2007). Wouter Van der Brug and Joost Van Spanje (2009) argue that a number of policy dimensions relate strongly to the left–right dimension, including the economic, the green-alternative-libertarian versus traditional-authoritarian-nationalist (gal-tan) and migration dimension. While the economic dimension is usually regarded as typically ‘left–right’, it is less suitable to distinguish between left- and right-wing populists, because on socio-economic issues right-wing populist parties have sometimes taken a more market-oriented and sometimes a more state-oriented position, as we argued above (De Lange, 2007). In a number of European countries, including the Low Countries and Scandinavia, both left- and right-wing populists support the welfare state. Instead, we focus on the issue of migration, which is strongly connected to radical right-wing populism, but not so much to left-wing populism, as anti-immigrant policies are part of the radical right and not of populism itself (Mudde, 2007). Therefore, we would expect left-wing and right-wing populist parties to behave relatively dissimilarly on this issue. If we do indeed find that left-wing and right-wing populists do not behave alike on the issue of migration, this would strengthen the argument that negativity towards others is indeed a characteristic of radical right-wing (populist) parties rather than populism per se.

H3: Migration hypothesis. Left-wing and right-wing populist parties will behave less alike on the issue of migration than on other issues.

Comparing Left-Wing and Right-Wing Populists: SP and PVV

The Netherlands is the only West European country where a left-wing and a right-wing populist party were in parliament together: to identify parties as populist we rely on the classification of parties by other authors (De Lange, 2008; Hakhverdian and Koop, 2007; March and Mudde, 2005). As can be seen in Table 1 quite a few West European countries have right-wing populist parties represented in their national parliaments, but not many parties are explicitly labelled as ‘left-wing populist’: the only parties that have been in a West European parliament and received this label are the Dutch SP, Sinn Féin in the Republic of Ireland and the German PDS/Die Linke.1 As no right-wing populist party has yet entered the Irish Dáil or German Bundestag, the Netherlands is the only case in which one can directly compare the behaviour of left-wing and right-wing populist parties. Four left-wing populist/right-wing populist combinations are possible: CD–SP, LPF–SP, LN–SP and PVV–SP. We select the pair PVV–SP because this pair of parties was in parliament for the longest period of all possible pairs, namely continuously since 2004.2

Table 1. Left-Wing and Right-Wing Populist Parties in Western Europe
CountryLeft-wing populistRight-wing populista
  1. Note: The table only includes parties with national parliamentary representation.
  2. aIncludes both neo-liberal and radical right-wing populists.
  3. bAuthors' additions.
  4. cNot populist during the entire period.
  5. dSF candidates are elected to the House of Commons but do not take their seats.
Sources: De Lange, 2008; March and Mudde, 2005; Hakhverdian and Koop, 2007.
Austria FPÖc1949–now
Belgium FN1991–2010
Denmark FrP1973–2001
Finland PSc1966–now
France FN1986–93



Italy FI/PdLb1994–now
Luxembourg ADRb1989–now
NetherlandsSP1994–nowCP/CD1982–6, 1989–98
Norway  FrP1973–7
Sweden ND1991–4
Switzerland APS/FPS1987–99
United KingdomSFbd1983–now 

In the Netherlands there are three centre parties: the Christian Democratic Appeal (CDA), the People's Party for Freedom and Democracy (VVD) and the Labour Party (PvdA). The PvdA and the VVD disagree on socio-economic policy, while the PvdA favours state intervention and the VVD supports free-market policies. The CDA takes a centrist socio-economic position. It is more conservative than the PvdA and VVD on moral issues and democratic reform. These three parties favour European integration. They form the core of governing coalitions: between 2003 and 2006 the coalition was formed by the CDA and the VVD, joined by the progressive liberal Democrats 66 (D66), which has a centrist socio-economic position and a progressive position on moral issues and democratic reform. Between 2006 and 2010 the CDA and the PvdA were joined in government by the economically centrist, Eurosceptic and morally conservative Christian Union (CU). Other parties with parliamentary representation include the Political Reformed Party (SGP) with an orthodox Christian profile, Green Left (GL), a left-wing, environmentalist, pro-European party, and the Party for the Animals (PvdD), which focuses on animal rights. Between 2002 and 2006 List Pim Fortuyn (LPF) was also in parliament. This was a right-wing populist party like PVV, although its anti-immigrant and anti-EU positions were less radical; it lost all its seats at the 2006 elections.

This leaves SP and PVV. For both parties there is debate on the degree to which they qualify as ‘populist’, which also varies over time. The Socialist Party (SP) was formed as a Maoist splinter party in 1971 (Koole, 1995). In its early years, SP followed a Maoist strategy: party members were required to integrate into the masses to learn ‘what the people wanted’ (Voerman, 1987). After failing to enter parliament in five consecutive parliamentary elections, the party adapted, abandoning its Maoist strategy and Marxist ideology (Lucardie and Voerman, 2012; Van der Steen, 1995; Voerman, 1987). By 1994, the party had reinvented itself as a left-wing protest party: it entered the election with the slogan ‘Vote Against, Vote SP’ (Lucardie and Voerman, 2012, authors' translation). It won 1 per cent of the vote, enough for two seats. SP increased its vote share considerably up to 2006, when it became the third party in parliament (17 per cent of the seats). It currently holds 10 per cent of parliamentary seats. During the 1990s and 2000s SP moderated its policy positions: in 1999 the party abandoned the idea that socialism was the end phase of history (Voerman and Lucardie, 2006). The party also moderated its populist anti-system rhetoric (De Lange and Rooduijn, 2011; Rooduijn and Pauwels, 2011; Voerman, 2011, p. 198). The party now strongly emphasises democratic governance: the democratically legitimated Dutch government should be protected against encroachment from technocratic European decision making and against privatisation, which moves decision-making power to the market (Voerman and Lucardie, 2006).

Different authors have debated the extent to which SP can still be characterised as a populist party. Recent overviews of populist parties still include SP (Hakhverdian and Koop, 2007; Lucardie and Voerman, 2012; March, 2011; March and Mudde, 2005). Sarah De Lange and Matthijs Rooduijn (2011, p. 328) observe that, while many references to ‘the (sovereign) people’ remain, there are lower levels of anti-elitism in SP's election manifestos of 2002 and 2006. Paul Lucardie and Gerrit Voerman (2012, pp. 64–7) and Luke March (2011, p. 130), however, still observe key features of populism, anti-elitism and appeals to popular sovereignty in the party's rhetoric. One example of this is the party's 2010 election manifesto, which started with the words:

Politicians have failed, you have the chance to speak now. … The people we gave our trust took irresponsible risks. Bankers, speculators, managers and shareholders enriched themselves and those who were supposed to regulate them turned the other eye. … Never before did we see such a painful unmasking of the political and economic elite (SP, 2010, p. 5).

Elsewhere in the manifesto the party states: ‘In a democracy, you have the last word. But you have been given increasingly less power. … People should have more to say about what belongs to all of us’ (SP, 2010, p. 11). The 2010 manifesto called for a national binding referendum, increased use of local referenda and reforms to give citizens more power over their MPs. Moreover, SP's campaign against the EU constitution, in which the party warned against becoming a powerless province in an undemocratic European Union, is regarded as an example of its populist stance (Lucardie and Voerman, 2012, p. 65). In addition, the party leader continued to make anti-elite statements, such as, in 2008: ‘They promise a lot in the Hague, but they fail to deliver while they are very good at caring for their own interests’ (cited in Lucardie and Voerman, 2012, p. 66). Therefore, we conclude that the key features of populism – anti-elitism and appeals to popular sovereignty – are still visible in SP's rhetoric.

There is considerable discussion about how to characterise the ideology of the right-wing PVV (Lucardie, 2009). PVV was formed as a split-off party from the liberal VVD (Lucardie and Voerman, 2012). The party founder and leader Geert Wilders had been an MP for the VVD since 1998. Over the course of the 2000s Wilders' ideology developed considerably (Vossen, 2011). Before 2002, Wilders was a follower of conservative-liberal VVD leader Bolkestein who combined economic liberalism with reservations about migration and European integration. After the 2002 elections Wilders became an important voice in the debate on integration, immigration and Islam, moving in a neo-conservative direction (Vossen, 2011): he criticised the ‘progressive’ Dutch political elite for neglecting the growing threat of Islam. He advocated closing down radical mosques and denaturalising migrants who refuse to integrate into Dutch society (Lucardie and Voerman, 2012). This put him at odds with the VVD leadership. The breaking point between Wilders and the VVD was the question of whether Turkey could become a member of the EU, which the VVD favoured but Wilders opposed. Wilders left the VVD and continued as an independent MP after 2004. Even though Wilders criticised the political elite and identified an external threat, Vossen does not consider Wilders as populist in this period because Wilders said that ‘the Dutch population had become inert, vulgar and soft’ as a result of progressive indoctrination (Vossen, 2011, p. 183). Wilders continued to support neo-liberal economic measures such as reducing welfare state spending (Lucardie, 2009). Wilders formally founded the Freedom Party (PVV) in 2006. In that year PVV won nine seats (out of 150) in the parliamentary election. It moved in a national-populist direction (Vossen, 2011); Wilders began to refer more and more to the common people and he became more supportive of direct democracy. PVV moved away from its original liberal economic position on economic affairs and PVV now opposes raising the retirement age, supports increasing spending on care for the elderly and opposes labour market liberalisation. In the 2010 general election the party increased its share of the vote from 6 per cent to 16 per cent. PVV entered into an agreement with the CDA and VVD to support their minority cabinet between 2010 and 2012.

While authors disagree about the extent to which SP and PVV can be considered populist over time, there is a general agreement in the literature that these two parties can both be considered populist. In the remainder of the analysis we will work under the assumption that PVV and SP can both be characterised as populist.

Data and Methods

We use data on parliamentary voting behaviour in the Netherlands in the period 2004–10. The study of parliamentary voting behaviour is well suited for our particular research question. As parties vote on the same issues, voting behaviour is a good indicator of how often these parties behave in a similar way. Of course, voting is only a small part of what parties do in parliament, but it is a crucial part, because it represents the ultimate decisions parliamentary parties make.

Our analysis of parliamentary votes focuses on voting behaviour by parties, rather than individuals, because party unity is extremely high in the Netherlands (Andeweg and Thomassen, 2011). In fact, party unity is so much the norm that it is common practice for MPs to vote by a show of hands and the results are normally recorded by party (Bovend'Eert and Kummeling, 2010).

As is the case in most parliamentary systems with a majority government, the voting behaviour of parties in the Dutch parliament is influenced strongly by the government–opposition divide. Whereas government MPs are bound by the coalition agreement, MPs from opposition parties can sponsor and favour any proposal they like (Holzhacker, 2002). Moreover, opposition parties tend to be more active than coalition parties when proposing motions and amendments, because they will be more dissatisfied with government policies than coalition parties are. As both SP and PVV were in opposition during the period studied here (2004–10), we effectively control for the influence of the coalition–opposition divide.

This article analyses votes on amendments and motions, which represent a large majority of parliamentary votes.3 We draw our data from the official parliamentary records (Ministry of Home Affairs and Kingdom Relations, 2011). We obtained parties' voting behaviour by computer processing the parliamentary records via custom-built software. Next, we obtained the text and policy classification of the proposals that were voted on from the official records. While this classification scheme was useful for the issue category of migration, it proved to be inadequate for the democratic reform and European integration categories. A large part of the proposals that were officially categorised as ‘governance’ were either of a very technical nature or had only a weak connection to the topic. Many of the proposals that were classified as ‘European’ had a link with the European Union, but did not concern the question of European institutions, furthering EU integration or EU enlargement. Therefore, we made a more specific classification of these proposals by hand. We broke down the 1,076 ‘governance’ proposals into the following categories: ‘Democratic reform: direct democracy’, ‘Democratic reform: participation’, ‘Democratic reform: other’, ‘Governance: bureaucracy’, ‘Governance: civil servants’ and ‘Other’ (see Appendix A). The 439 proposals relating to Europe were classified in the following categories: ‘EU institutions’, ‘EU enlargement’, ‘EU policies’ and ‘Other’. A small proportion of the proposals were coded by a second coder to test for inter-coder reliability (following the method of Krippendorf, 2004), which proved satisfactory.4

We analyse voting behaviour in two ways: first, we simply look at the proportion of proposals on which parties vote the same. Second, in order to compare the patterns in voting more precisely we use Optimal Classification (OC), a method developed for spatial analysis of party positions. This allows us to assess not only the (dis)similarity in the voting behaviour of SP and PVV, but also what sets them apart from the other parliamentary parties. Is the structure of the political competition different on those issues that relate to the core of populism? The OC algorithm induces party positions from their voting behaviour. It tries to position parties in a low-dimensional spatial model. Parties that often vote together will be positioned close to each other and parties that are very dissimilar in terms of voting behaviour are at a large distance from each other in the spatial model. An OC model can be either one-dimensional (for example, an ordering of parties from ‘left’ to ‘right’) or multidimensional. A simple one-dimensional model would be the following. Consider that there are three parties that voted only twice. Party A supported both proposals, party B rejected them both and party C voted for one of them. In this case we can order the parties in the following way: A, C, B. Parties A and B are positioned furthest away from each other (as they voted differently on both proposals) with party C in the middle.

The OC algorithm calculates the party positions in such a way that each parliamentary vote can be drawn as a dividing line between those parties that voted ‘yes’ and those parties that voted ‘no’ (Poole, 2000; 2005). In our simple example the dividing line for the first vote would run between party A on the one side and party C and B on the other side and the dividing line for the second vote would lie between party A and C on one side and party B on the other side: A | C | B. In this example it is easy to determine the positions of parties and the dividing lines of votes without making any errors. Of course, when analysing voting behaviour for many parties on a large number of issues, there will always be votes that do not fit with such a simple model, for example when an otherwise centrist party votes against all the other parties. The OC algorithm positions parties and dividing lines in a way that minimises these errors. It results in a spatial model of party positions in which parties that vote similarly are positioned closely together and parties that vote dissimilarly are positioned far away from each other. The dimensionality of these models is determined by the level of error. One attempts to find a model with a minimal number of dimensions and limited error, which is measured by the Aggregate Proportional Reduction in Error (APRE). This is the percentage of correctly classified vote choices corrected for the fact that votes can be lopsided. The APRE expresses the extent to which the estimate performs better than a random assignment of the parties based on the distribution of the votes (Poole, 2005, p. 129). All models used have an APRE of at least 0.8. It is important to note that the dimensions of the resulting space have no a priori substantive meaning: it is the distances between parties that are relevant and which can help us to interpret the meaning of the dimensions.

We model voting in a legislature in which there are effectively only around ten actors, namely the parties. In these situations the use of Optimal Classification, which only requires a minimal number of assumptions, is more appropriate than the use of parametric algorithms for estimating party ideal positions (Rosenthal and Voeten, 2004).


We are interested in the question of whether populist parties vote more alike on issues that relate to the core of populism than on other issues. Thus, before we turn to the analysis of specific issue areas, we first have to establish a baseline. Over the whole 2004–10 period, SP and PVV voted the same way in 44 per cent of the cases. In comparison with the extent to which other parties vote alike, this percentage is low. This supports the assertion that if populism is an ideology, it is indeed thin. Voting behaviour in the Dutch parliament seems to be structured to a large degree by left–right patterns. Figures 1 and 2 display the extent to which parties vote the same as SP and PVV, respectively, expressed as the percentage of cases in which two parties voted the same. Between 2004 and 2010, the voting behaviour of SP was matched most closely by GL, which voted the same in 85 per cent of cases. In declining order we then find the left-wing PvdD and PvdA, the centrist D66, CU, SGP and CDA and the right-wing LPF. PVV takes the second lowest place – only VVD shows voting behaviour that is more dissimilar to that of SP. When we order parties according to the degree to which they voted the same as PVV, we find the opposite ordering of parties (Figure 2). LPF voted the same as PVV in 74 per cent of cases, while VVD voted similarly as PVV in 72 per cent of cases. This percentage gradually declines as we move to the left of the graph, dropping to only 44 per cent for SP and 41 per cent for GL and the PvdD. We find that on the whole the voting patterns of PVV and SP are very dissimilar. This shows that PVV and SP are ideological opposites: one on the far left and one on the far right.

Figure 1.

Votes the Same as SP 2004–10 (%)

Note: The black dotted line indicates the mean percentage of voting with SP.

Figure 2.

Votes the Same as PVV 2004–10 (%)

Note: The black dotted line indicates the mean percentage of voting with PVV.

This assessment is supported by an OC analysis of parties' voting behaviour (see Figure 3a). The level of the error as expressed by the APRE justifies a two-dimensional model. Figure 3a shows the party positions in the resulting spatial model. The OC analysis constrains the party positions to lie within the circle dotted in grey. The axes of the scatter plot have no predetermined meaning because OC is an inductive procedure, but it is relatively straightforward to interpret the differences between the parties. Parties are positioned from ‘left’ to ‘right’ on the horizontal dimension, while the vertical dimension displays a government/opposition divide. The three parties that formed the government during approximately three years out of the six that we are studying (CDA, PvdA and CU) are positioned towards the bottom of the figure. To the top left of the figure we find the left-wing opposition, including SP. The right-wing opposition, including PVV, is positioned at the top right of the figure. It is important to note that the horizontal dimension of the figure is much more important than the vertical dimension: more votes set apart ‘left’ from ‘right’ parties than ‘government’ from ‘opposition’ parties.5 Thus, while SP and PVV in general vote the same on a few issues, they vote differently on most.

Figure 3.

Optimal Classification Estimates of Party Positions

  • (a) All VotesNote: N = 8,412 (1,203 unanimous votes deleted), % correctly classified = 95%, APRE = .84.
  • (b) Votes on GovernanceNote: N = 410 (72 unanimous votes deleted), % correctly classified = 95%, APRE = .81.
  • (c) Votes on Europe/EU InstitutionsNote: N = 100 (10 unanimous votes deleted), % correctly classified = 96%, APRE = .86.

Our expectation is that while in general PVV and SP voted differently, they would vote more alike on specific issues linked to their populist agenda, especially when it comes to democratic reform and European integration. Table 2 shows the degree to which PVV and SP voted alike on these issues between 2004 and 2010. Our first hypothesis concerns the issue of democratic reform. We distinguish between three categories of democratic reform: measures promoting direct democracy, measures designed to enhance political participation and other reforms. While we would expect that populists agree mostly on the issue of strengthening direct democracy, we only see a moderate level of agreement between SP and PVV on this issue (50 per cent), only six percentage points more than the two parties agree on average. Both parties supported, for example, abolition of the Senate and the citizens' initiative to bring issues to parliamentary discussion, but they disagree on the need to allow more constitutional review. This is, however, based on an analysis of only eight votes, which at least tells us that direct democracy is not a major concern for these parties as it would have been relatively easy to table more parliamentary motions on the subject if it had been central to them. SP and PVV do vote alike more often on issues that concern participation (71 per cent), for example when they opposed the Cabinet's ‘100 days tour’ which was designed to reach out to society but was perceived merely as propaganda by both PVV and SP. On other democratic reforms PVV and SP disagree more often than they do on average across all votes. We also looked at parties' voting behaviour on the issue of governance, in particular the issues of (decreasing) bureaucracy and the position of civil servants. Here we do observe a higher than average agreement between SP and PVV. Thus, regarding votes on democratic reform, the evidence is mixed: on most topics relating to governance and democratic reform SP and PVV agree more often than they do on average across all votes. Nevertheless, this does not hold (at least not as strongly) for the theoretically important subcategory of direct democracy. Furthermore, the fact that SP and PVV vote more alike on an issue may simply be the result of a higher consensus across the board: all parties might agree more on particular issues. For example, Table 2 shows that all parties vote alike on average in 74 per cent of the votes on participation; 12 percentage points above average. Also, when voting on issues concerning bureaucracy, all parties vote more alike. Opposition parties may also vote more similarly on specific issues. Table 3 shows that the parties that were in opposition during the whole 2004–10 period voted more alike on the issue of direct democracy than they did on average. Thus, this suggests that some of the voting similarity between PVV and SP is the result of higher consensus among all opposition parties.

Table 2. SP and PVV Vote Alike (%)
ThemeCategoryN*Vote alikeDifference**
  1. *Absolute number of votes per category.
  2. **Difference from all issues. Positive values indicate that SP and PVV voted alike more often on an issue than they did on average; negative values indicate that they voted alike less often.
GovernanceDemocratic reform: direct democracy8506
Democratic reform: participation147427
Democratic reform: other3938−5
Governance: bureaucracy97539
Governance: civil servants1216016
EuropeEU institutions1106824
EU enlargement21484
EU policies15134−10
MigrationMigration and integration4719−25
All issues 9,61544 
Table 3. Average Agreement on Issues (%)
ThemeCategoryN*All partiesOpposition
Vote alikeDiff.**Vote alikeDiff.**
  1. *Absolute number of votes per category.
  2. **Difference from all issues. Positive values indicate that parties voted alike more often on an issue than they did on average; negative values indicate that they voted alike less often.
GovernanceDemocratic reform: direct democracy8621656
Democratic reform: participation1474127313
Democratic reform: other3959−257−2
Governance: bureaucracy97697655
Governance: civil servants121653634
EuropeEU institutions110610634
EU enlargement2157−454−6
EU policies15160−257−2
MigrationMigration and integration4758−452−8
All issues9,61562 59 

To test to what extent there is a difference between populist and non-populist parties, we have modelled parties' voting behaviour on all governance issues in Figure 3b.6 A visual comparison of Figure 3a (all votes) and Figure 3b (votes on governance issues) suggests that the patterns of voting behaviour are similar. SP and PVV are positioned slightly closer to each other, but not by much. Thus, in so far as voting behaviour of SP and PVV is more similar, this seems to be related to a stronger opposition–government divide on these issues rather than to a division between populists and non-populists. In the debate on democratic reform and governance, populist parties do not consistently set themselves apart from other parties.

The second hypothesis concerns European integration. We tested whether populist parties share an opposition to EU integration. To this end we look at three subcategories: institutions (should the EU be strengthened in terms of competences and institutions?), enlargement (should more countries be allowed to enter the EU?) and policies (substantive issues that had an EU dimension). We would expect that the two populist parties agree most strongly on the first category, European institutions. The data support this expectation: SP and PVV voted alike on 68 per cent of the proposals in this category, which is 24 percentage points higher than their average. Both parties opposed, for example, the Lisbon Treaty and voted against transferring policy competences to the European Union. On EU enlargement, SP–PVV voting agreement is slightly higher than their overall voting agreement (4 per cent higher than their average). With regard to substantive issues with an EU dimension, the two parties vote relatively differently (34 per cent agreement). This shows that while the two parties share a (negative) outlook on EU integration, when it comes to the substantive issues they have very different perspectives. Table 3 shows that overall (opposition) parties do not vote much more alike on Europe than on other issues.

The OC analysis of parliamentary votes on European institutions/sovereignty dimension shows that parliamentary votes on Europe are structured rather differently than votes on other issues (Figure 3c). On the bottom left-hand side of Figure 3c we find parties that are generally in support of further European integration. To the right we find the parties that oppose strengthening EU powers most strongly: SP and PVV. There is no evidence of a left–right divide in these votes. There are some indications that the government–opposition divide does play a role in votes on the European Union. Consider, for example, the position of the generally Eurosceptic CU. It stands very close to its coalition partners: CDA and PvdA. Thus the voting on the EU is structured along a different dimension than the usual left–right pattern. The horizontal dimension, on which SP and PVV are positioned closely together, is more important in explaining votes than the vertical dimension, on which the two parties are placed further apart. All in all, the data corroborate our hypothesis: on the issue of EU institutional integration, SP and PVV vote more alike. Moreover, the data set these parties apart from the non-populist parties, except the Party for the Animals (PvdD).

Concerning the issue of migration, which is linked rather strongly to left–right politics in the Netherlands, we expected to find only a limited degree of similarity between SP and PVV. And indeed, the two parties vote very differently on this issue, voting alike in only 19 per cent of the votes. This is well below their average agreement in voting. While overall parties agree less on the issue of migration than on other issues (−4 per cent), the effect is much stronger for SP and PVV (−25 per cent). This issue reflects PVV's restrictive immigration policies and tough civic integration policies, specifically oriented towards Islamic migrants. On these issues SP and PVV stand diametrically opposed. Moreover, the disagreement on this issue has actually increased over time, as PVV became more Islamophobic (Vossen, 2011). Despite its tradition of being critical of migration and a perception among the electorate of a relatively tough stance in this area, SP does not even come close to the position of PVV. Therefore the hypothesis that PVV and SP behave less alike on migration than on other issues is corroborated.

Discussion and Conclusion

What is more important in motivating the behaviour of left-wing and right-wing populists: their populism or their position on the left–right spectrum? This article compared the behaviour of two political parties that are generally recognised as populist, that use the same populist rhetoric but stand at opposite ends of the left–right spectrum. In general, SP and PVV vote very differently: the left-wing populist SP votes in the same ways as the other parties of the left, while the right-wing populist PVV votes in the same way as the other parties of the right. It does not appear to be the case that populism is the driving force behind their parliamentary voting behaviour. We expected PVV and SP to behave more similarly on a limited number of issues that form the core of populism: democratic reform and European integration. This expectation is only partially met. The strongest match between SP and PVV voting behaviour is on questions surrounding the transfer of sovereignty to the European Union. SP and PVV do not only agree in words that the Netherlands should not transfer sovereignty, but also agree in actions. On the issue of democratic reform, SP and PVV show slightly more similarity in voting behaviour than on other issues. SP may have moderated its anti-elite rhetoric, as others have observed (Lucardie and Voerman, 2012), but there is still common ground with PVV on this issue. On left–right issues, such as migration, the parties' behaviour is clearly not similar, as we expected. It is the issue on which PVV and SP vote most differently. Clearly, PVV's critique of Islam and immigrants is not shared by SP. This provides empirical support for excluding negativity towards ‘others’, particularly immigrants, from the definition of populism. This is a part of radical right-wing populism rather than populism per se.7

This study is the first to contrast the behaviour of left-wing and right-wing populist parties in parliament. It shows that their left-wing or right-wing ideology is more important in guiding their behaviour than their populism. It does not provide a definitive answer to the similarity between left- and right-wing populists: left-wing and right-wing populists may act differently depending on the party system and the political system of a particular country (Hakhverdian and Koop, 2007), which makes us cautious about generalising our findings beyond the country studied. Nevertheless, our finding that SP and PVV vote similarly on European integration but not at all on migration poses a challenge to the argument that European politics is increasingly structured by a single socio-cultural dimension, consisting of both migration and European integration (Kriesi et al., 2008). Our findings suggest that at least in Dutch parliamentary behaviour the two dimensions do not correlate very strongly, confirming previous findings by Van der Brug and Van Spanje (2009).

Our results sustain the idea that populism as a thin or partial ideology can be combined with different political positions. For the populist parties that we examined their diverging positions on the left–right dimension are more important for their behaviour than their shared populism. These results sustain the argument of Mudde (2007) that the term ‘populist radical right’ is more appropriate than ‘radical right populism’, because they are primarily radical right-wing parties. For these parties their policies on immigration are more important than their populism. Something similar can be said for the populist radical left parties such as SP. This finding stands in contrast to Hans Keman and Paul Pennings' (2011) analysis, which found a strong similarity between the election manifestos of PVV and SP. Their parliamentary voting behaviour, however, appears to be quite different. Our finding is in line with those of expert surveys, which put PVV and SP at opposite ends of the political spectrum, but find more similarity for specific issues (Hooghe et al., 2010). When assessing party positions experts do not simply look at the rhetoric in their election manifestos, but may also take their actual behaviour in parliament into account. Our analysis suggests that while PVV and SP may share a common populist rhetoric, their parliamentary behaviour is very different.

Our analysis demonstrates that complementing existing methods of positioning populist parties by studying their actual behaviour in parliament allows us to determine more precisely not only populists' political rhetoric and electoral stance taking, but also how they operate in the parliamentary setting. This allows researchers to assess much more precisely the differences and commonalities between left-wing and right-wing populism. The analysis of voting behaviour provides new insights because it allows us to compare parties' responses to the exact same proposals. While in countries with only a right-wing populist party a direct comparison between left-wing and right-wing populists is impossible, one may still be able to compare the behaviour of right-wing populists with, for example, other right-wing parties on issues that belong to the core of populism. Furthermore, MPs have a range of tools at their disposal that may extend this type of analysis in the future, such as parliamentary questions, parliamentary speeches and the sponsorship of motions. In future work, students of populism may want to use these sources more extensively, not only to study the differences between left-wing and right-wing populism in specific countries, but also to compare populist parties' parliamentary behaviour across borders.

Appendix: Appendix A: Manual Recoding of ‘Governance’ and ‘Europe’ Issues

CategoryRefined classificationDescription
GovernanceDemocratic reform: direct democracyProposals to introduce referenda, increase the number of elected offices
Democratic reform: participationProposals to increase citizens' participation in public policy making via intermediary organisations (parties, interactive policy making)
Democratic reform: otherOther references to democratic reform, such as strengthening parliamentary control
Governance: bureaucracyProposals to decrease bureaucracy, regulation
Governance: civil servantsProposals to change the position of civil servants as well as the payment of public office holders
OtherOther proposals concerning governance, including proposals on the internal functioning of parliament
EuropeEU institutionsProposals regarding the competences of the EU and the organisation of EU decision making (intergovernmental/supranational)
EU enlargementProposals regarding EU enlargement with new Member States
EU policiesProposals that are mainly concerned with substantive issues that are already under EU competence (or where EU competence is not disputed)
OtherOther issues relating to European affairs.


We thank Sarah de Lange, Koen Vossen and the anonymous reviewers of this journal for their critical comments and useful suggestions in writing this article.

  1. 1

    The Scottish Socialist Party is also mentioned often. This party has only held seats in the Scottish Parliament, in which there is no right-wing populist party. Sinn Féin, next to its representation in the Republic of Ireland, also has elected representatives in the House of Commons, but they do not take their seats as they refuse to pledge allegiance to the Queen.

  2. 2

    It would also have been possible to examine the voting behaviour of LPF and SP, which have been in parliament together between 2002 and 2006. The problem is, however, that between 2003 and 2006 LPF fell apart into different political groups that did not vote in the same way. PVV was not officially founded until 2006; we consider the behaviour of its founder and leader Wilders, who sat as an independent MP between 2004 and 2006, as the party line before 2004. This allows us to study a longer time frame, which includes relevant debates regarding the European constitution and the EU referendum. The findings would, however, not have been substantially different if we had studied the 2006–10 period.

  3. 3

    We excluded votes on bills, because most of these votes are near unanimous.

  4. 4

    A Krippendorf's alpha of 0.792 for the ‘governance’ proposals and 0.845 for the ‘Europe’ proposals.

  5. 5

    This can be learned from a visual inspection of the cutting lines (not displayed).

  6. 6

    The number of votes on democratic reform alone was too small (n = 8) for a separate analysis.

  7. 7

    Of course, one could argue that SP is also negative towards ‘others’, but that they define others in different terms (such as ‘bankers’ or ‘capitalists’). If one makes that argument, however, the meaning of the term ‘negative towards others’ should be specified, because many political parties are critical of particular groups in society.


  • Simon Otjes is a Researcher at the Dutch Political Parties Documentation Centre, Groningen University. His research interests include political parties and party systems and parliamentary politics. His work has appeared in the American Journal of Political Science, Party Politics and Res Publica. Simon Otjes, Groningen University, Dutch Political Parties Documentation Centre, PO Box 559, 9700 AN Groningen, the Netherlands; email: s.p.otjes@rug.nl

  • Tom Louwerse is Assistant Professor in Political Science in the Department of Political Science, Trinity College Dublin. His research interests include political representation, legitimacy, political parties and parliamentary politics. Tom Louwerse, Department of Political Science, Trinity College Dublin, 3 College Green, Dublin 2, Ireland; email: Tom.Louwerse@tcd.ie