What Would the British Party System Look Like under Proportional Representation?

British debates over electoral reform are invariably debates about what party system would emerge. While there is agreement that proportional representation (PR) would boost the size of existing smaller parties, there is no consensus over the emergence and prospering of new parties. The main weakness in the British debate concerns the types of governments that would form under PR. Some believe the Liberal Democrats would be perennial kingmakers. Others suggest that a ‘ progressive alliance ’ on the centre-left would sweep all before it. This article considers the experience of west European multiparty systems since the 1980s and argues that party system fragmentation and the growth of non-centrist parties would characterise Britain under PR. Moreover, the pattern of overlapping centrist coalitions seen in Germany and Benelux would be unlikely to emerge in Britain. Instead, a two-bloc system, common in Scandinavia and southern Europe, would most likely develop.

OVER A DECADE has passed since Britain's referendum on changing the voting system saw voters stick with the status quo, but the debate over electoral reform continues. 1roportional representation (PR) has been a long-standing demand of parties disadvantaged by Britain's plurality system, or first past the post (FPTP).Foremost among these parties are the Liberal Democrats, the traditional 'third' force of British politics, as well as the Greens.A minority within the Labour Party has supported PR, usually in electorally fallow times, although it won the backing of delegates at the 2022 party conference.Labour's leadership generally prefers the bounty that FPTP (sometimes) delivers.Very few figures in the Conservative Party advocate PR, reflecting the party's success under FPTP over the last century.
Today, most voices calling for PR are on the centre-left.Neal Lawson, director of the thinktank, Compass, has described a 'latent progressive majority' comprising those who vote for Labour, the Liberal Democrats and the Greens, which could form a 'progressive alliance' under PR.According to Lawson, this alliance would ensure 'the Tories can never govern again without a majority of the country backing them'. 2 Political developments since the 2011 referendum, which offered voters the nonproportional 'alternative vote', have extended support for PR.The left-wing Labour pressure group, Momentum, advocated voting reform in 2021.Keir Starmer's purge of Jeremy Corbyn and his allies may lead other supporters of the former Labour leader to reassess the merits of an independent radical-left party under PR. 3 On the other side of the spectrum, the rise of the populist UK Independence Party (UKIP) and more recently the Brexit Party has led right-wing figures such as Nigel Farage to advocate PR.Farage noted how UKIP won 1 3.9 million votes in the 2015 general election for just one parliamentary seat.PR would have delivered eighty-three; it may have been more because some potential UKIP voters were dissuaded by fear of 'wasting' their votes under FPTP, that is, voting for candidates that have no chance of winning a plurality in a given constituency.Contra Lawson, Farage predicted 'a coalition of common sense' would form between the Conservatives and a UKIPtype party under PR. 4 As this overview shows, the debate over PR is really a debate about the party system it would produce.This article eschews discussion of the relative merits of different voting systems-it merely assumes a generic form of PR.Instead, it focusses on the shape of Britain's party system under PR.The paper considers trends in west European multiparty systems, particularly fragmentation and the growth of non-centrist parties, and assesses their likelihood in Britain under PR.It also highlights the pattern of cabinet formation and alternation as a key factor shaping multiparty British politics.

Party systems and patterns of government formation
Much of the British debate on electoral reform adopts Maurice Duverger's classic contrast of two rival sets of institutional linkages.Thus, while FPTP produces two-party systems and single-party majority governments, PR produces multi-party systems and coalition governments.The debate proceeds over whether governments should be chosen directly by voters in elections (FPTP), or emerge from negotiations among party elites in a parliament that is a microcosm of society (PR). 5lthough there is some truth in this contrast, it is overly simplistic.In particular, European multiparty systems do not all function alike, even those with identical electoral systems.Giovanni Sartori defined a party system as a 'system of interactions resulting from interparty competition'. 6The focus of these interactions is the formation of cabinets.Thus, Peter Mair described party systems as 'structures of competition for government'. 7This term incorporates several aspects of cabinet formation: whether party alternation in government is usually wholesale or partial; whether governing alternatives are consistent over time or innovative, with new coalitions regularly tried; and whether access to office is restricted to some parties or open to all. Figure 1 illustrates different party systems and their contrasting patterns of government formation and alternation.
In two-party systems (1.1), the governing alternatives are a single-party social-democratic majority cabinet or a single-party conservative one.The parliamentarians within these two parties occupy the full range of the ideological spectrum, as radical-left and -right politicians must work within the existing catch-all parties.One party governs alone until it loses an election and is replaced by its opponent.Alternation is wholesale.The British case approximated this model in the postwar era, although less so in recent years with greater third-party representation and the 2010-15 Conservative-Liberal Democrat coalition.
The governing alternatives in a simple multiparty system are shown in 1.2.This one depicts Sartori's classic case of 'moderate pluralism', where fragmentation is low (three to five parties), ideological distances between parties are small, and 'overlapping' cabinet alternatives are available. 8This captures the West German party system from the 1960s to the 1980s.Two major catch-all parties, the social-democratic SPD and the Christian-democratic CDU/CSU, competed for the support of a smaller liberal 2 TH O M A S Q U I N N party, the FDP, to provide a legislative majority.Government alternation is partial, as the centrist party exchanges one major party for the other.
Another Sartorian multiparty category, 'polarised pluralism', is shown in 1.3.Originally applied to postwar Italy, it entails a more fragmented system (six to eight parties) in which broadly centrist governments face 'bilateral' oppositions of far-left and far-right permanently excluded from government.Sartori viewed the latter as 'anti-system' parties pursuing a non-democratic regime, that is, communists and neo-fascists.
The rise of contemporary radical-left and radical-right parties invites comparisons with polarised pluralist systems in some countries.There are differences: these parties are not anti-systemic, as they are committed to democracy.But they are anti-establishment, populist and willing to make argumentsand use language-not used by the mainstream. 9When mainstream parties collectively T Ideologically overlapping and partially alternating cabinets are not the only possibility in multiparty systems.In Scandinavia, and now southern Europe, a more common pattern involves parties dividing into two ideological blocs, offering voters a choice of governing coalitions.These blocs can be formal alliances or loose associations.Elections in Norway, Sweden and Denmark usually entail left and right ('red' and 'blue') blocs contesting power.The system was partly a consequence of the previous era of socialdemocratic hegemony that compelled centrist and right-wing parties to join forces.As the social-democratic parties declined, and green and radical-left parties grew, multiparty left blocs formed to face their respective right blocs. 10 In contrast to this organic emergence, Italian elites purposely adopted 'bipolarism' after a corruption crisis destroyed the old party system in the 1990s.Spain, Portugal and Greece did likewise after their return to democracy in the 1970s.
A two-bloc system encompassing all parties is shown in 1.4.Radical-left and radical-right parties are incorporated into the blocs.Cabinets are single-bloc affairs, formed by whichever bloc wins a legislative majority.Parties in the majority bloc could decide to form a minority cabinet, containing only some of them.Thus, radical-left or radical-right parties might be excluded from the cabinet by the mainstream parties, but offered policy concessions on salient issues in return for confidence-and-supply support to a minority government.Alternation in office is usually wholesale when one bloc loses an election and is replaced by the other.Overlapping cabinets generally do not occur unless a centrist party defects from one bloc to the other.However, this is typically infrequent and the party would be expected to signal such a shift before an election.

Europe's fragmenting party systems
The previous section presented three generic multiparty systems, each differing in their pattern of cabinet formation.Before assessing which would likely emerge in Britain under PR, it is worth considering some relevant continental trends.As partisan dealignment loosened bonds between voters and older parties in recent decades, west European multiparty systems fragmented. 11Older catch-all parties shrank and new ones emerged, many of them ideologically radical. 12The effect has been to render classic moderate pluralism (1.2 above) less viable.
Table 1 shows party fragmentation in thirteen west European proportional democracies (semiproportional in southern Europe), plus the UK, in the 1980s and 2013-22.Fragmentation is captured by the 'effective number of parliamentary parties' (ENPP), a standard measure of 'relevant' legislative parties (thus, 2.0 indicates a two-party system, 2.5 a two-and-a-half-party system, and so on). 13Between these periods, ENPP doubled in Ireland and the Netherlands, and increased markedly in Spain, Austria, Sweden, Germany and Norway.Average ENPP in the thirteen proportional democracies increased from 3.7 to 5.3.The UK's 16 per cent increase would likely have been higher under PR.
One manifestation of fragmentation has been the splintering of previously strong social-democratic parties, as unionised manual workers declined in number and their partisan identities weakened.Some comparisons of legislative seats won during 1980-89 and 2013-22 are instructive.Germany's SPD fell from an average of 40.0 per cent of seats to 26.7 per cent; Austria's SPÖ from 46.4 per cent to 26.2 per cent; Spain's PSOE from 53.4 per cent to 29.9 per cent; Sweden's SAP from 45.9 per cent to 30.6 per cent; Denmark's SD from 31.3 per cent to 27.0 per cent; and the Dutch PvdA collapsed from 32.0 per cent to 6.0 per cent Many voters switched to green and radical-left alternatives.From 2013-22, the German Greens won an average 11.8 per cent of seats and the left-wing Die Linke 8.4 per cent; Austrian green parties 10.6 per cent; Danish greens 10.4 per cent and the Danish radicalleft 7.4 per cent.
On the right, Christian democrats were once hegemonic in the Low Countries, but secularisation has reduced them to minor party status.They have been supplanted by conservativeliberal parties.In Germany and Austria, the CDU/CSU and ÖVP are smaller than previously.Each lost support to radical-right parties, campaigning on immigration and crime.The latter also recruited working class voters from social-democratic parties.Radicalright parties barely existed outside Austria in the 1980s.During 2013-22, however, they won 22.2 per cent of seats in Austria, 17.6 per cent in Sweden, 16.7 per cent in the Netherlands, and 15.3 per cent in Denmark.Germany's AfD and Spain's Vox won average seat shares of 12.3 per cent and 10.9 per cent over their last two respective elections in this period.
These changes in party representation have had consequences for patterns of government formation.A major one is the decline of classic moderate pluralism in western Europe.As catch-all parties shrank and new entrants emerged on left and right, the mainstream parties had to decide how to respond.In many moderate-pluralist countries, green parties were invited into the governing cartel, but the radical-right and radical-left were penned behind a cordon sanitaire.Consequently, many countries with overlapping structures of government formation are now closer to contemporary polarised pluralism (Figure 1.3).
This pattern of revolving mainstream coalitions is evident in Germany, with its 'traffic light' (red-yellow-green) coalition of SPD, FDP and the Greens. 14A 'Jamaica coalition' (green-yellowblack) involves CDU/CSU replacing SPD.The Austrian government is a coalition of the centre-right ÖVP and the Greens.Germany and Austria both have recent experience of grand coalitions too.Similar patterns occur in Benelux with 'purple coalitions' (red-blue, referring to social-democratic and conservative-liberal parties), and 'purple-green' coalitions, the latter governing in Belgium and Luxembourg.The far-right and -left are behind a cordon sanitaire in all these states bar Austria, where the right-wing Freedom Party joined coalitions with ÖVP from 2000-06 and 2017-19.
In Scandinavia, radical-right parties were initially ignored and excluded by centre-right parties, as they maintained a cordon sanitaire.But as the radical-right grew, their legislative seats were needed and they were incorporated into the right blocs.Their admittance prompted the defection from the right of agrarian Centre parties to their respective left blocs, in Norway in 2005 and Sweden in 2022.Sweden's current minority cabinet contains Conservatives, Liberals and Christian Democrats, with confidence-and-supply support from the radical-right Sweden Democrats in return for influence, especially over immigration policy. 15imilarly, the radical left was initially shunned by the Norwegian Labour Party, but both governed together with the Centre Party from 2005-13.Cross-bloc cabinets are rare: one containing social democrats and liberals currently governs Denmark after three decades of bloc politics.But it remains to be seen how long the experiment lasts as the governing parties leak support to the 'bilateral' opposition. 16e shape of a British multiparty system This brief survey of western Europe offers two lessons for Britain.First, a proportional voting system will not simply lead to the closer matching of existing vote shares and subsequent parliamentary representation for the three main UK-wide parties and the SNP.Instead, freed from the problem of 'wasted' votes under FPTP, a dealigned electorate is more likely to shop around in a fragmented electoral marketplace, including for parties with little or no current representation.Secondly, these parties will face a collective choice between a polarised-pluralist and a two-bloc party system.Moderate pluralism, a staple of the British PR debate, is unlikely to be viable.

Fragmentation in Britain under PR
The number of parties would depend on the precise form of PR Britain adopted and the existence of thresholds for representation.However, the west European experience suggests that a post-reform British ENPP of 4.0-6.0would be feasible, with parties spanning the ideological spectrum.This would be at the expense of Labour and the Conservatives, which would be unlikely to avoid the Notably, there was no significant force on the British radical left.Its supporters generally organise within the Labour Party for fear of electoral oblivion as an independent force under FPTP.However, Labour's Corbynite takeover from 2015-19 indicated that the left's latent presence can become manifest in the right circumstances.Left-wing voices have increasingly made the case for PR, which would make a separate party feasible.
The centre-ground would probably change under PR.There is a significant ideological gap between the Liberal Democrats and the Conservatives.17Many European countries have a moderate non-conservative force on the centre-right, whether Christian-democratic or conservative-liberal (that is, classically liberal).It is doubtful that Christian democracy could emerge as a serious force in secular Britain.However, conservative-liberalism is an extant tendency in the Conservative Party, represented by some Tory Remainers (for example, those who formed Change UK in 2019).Under PR, they need not cohabit with socially conservative Eurosceptics.
A distinctive feature of the UK's party system is the presence of nationalist and unionist parties mobilised around the territorial cleavage.These could continue to exist under PR, as they do in Spain.These parties also adopt positions on the left-right divide, with Scottish, Welsh and Irish nationalists on the left, and Northern Irish unionists normally on the right.

Patterns of UK government formation under PR
The second issue concerns the pattern of government formation in Britain under PR.British debates on PR often assume a moderate-pluralist party system (Figure 1.2) would emerge.This assumption underlies claims that the Liberal Democrats would become kingmakers, putting Labour or the Conservatives in government.Yet, fragmentation and the growth of ideologically radical parties have made this type less viable in western Europe.The same would probably be true of Britain.As well as the growth of current minor parties, the European experience points to a party system in which Labour and the Conservatives were each down to 20-30 per cent of seats under PR.This alone would hinder a moderate-pluralist system because the large parties would be too small and the non-centrist parties too numerous and large.
That would leave either polarised pluralism or a two-bloc system.If the mainstream parties sought to construct a polarised-pluralist system, it would be with the intention of excluding the radical-left and -right from government formation.That would mean no deals with Reform UK or any new Corbynite party.The former would be vetoed by all parties on the centre-left; the latter by the Liberal Democrats and Conservatives.The pool of governing parties would consist of Labour, the Liberal Democrats, the Conservatives, probably the Greens, and possibly some unionist and nationalist parties.Any new conservative-liberal party could also be included.
In the absence of anchoring ideological blocs in Parliament, the governing parties would need to produce a majority from among themselves.If PR-based Britain mirrored European trends in fragmentation, even two-party majority coalitions would be hard to achieve.Among west European party systems with a structure of overlapping coalitions, as of 2023, Germany and Luxembourg had three-party governing coalitions, Finland a fourparty coalition (which replaced a five-party coalition), and Belgium a seven-party coalition (to balance linguistic groups).Mark Rutte's outgoing Dutch cabinet contained four parties.It is common for the major centre-left and centre-right parties to join together in coalitions, as with German and Austrian grand coalitions, and purple coalitions in Benelux.
Left-right coalitions are facilitated by the domination of the centre-right by Christiandemocratic (Germany, Austria, Luxembourg) or conservative-liberal (Belgium, Netherlands) parties.These party families, along with agrarian and social-democratic parties, have formed the governing basis of moderate-pluralist, and later contemporary polarised-pluralist systems.All four party families are relatively centrist, which facilitates cooperation. 18In contrast, traditional conservative parties like those in Spain, Sweden and Norway, are less centrist, and sometimes closer to the radical right.Compromises between conservative and social-democratic parties involve greater ideological trade-offs than when Christian-democratic and liberal parties dominate the centre-right.
Could this pattern of cabinet formation work in Britain under PR?There would be few difficulties between Labour, the Liberal Democrats and the Greens, the so-called 'progressive alliance'.There would be greater problems with the Conservatives, however.The Conservative-Liberal Democrat coalition of 2010-15 almost destroyed the smaller party, whose centre-left, anti-Conservative voter base was repelled by the deal.Would they want to repeat it?Furthermore, the ideological distance between conservatism and Labour's social democracy is wide.Yet, with a fragmented party system operating a cordon sanitaire to exclude the radical-left and radical-right, Labour-Conservative coalitions might be required for legislative majorities.As a non-centrist family, conservative parties like those in Norway, Sweden and Spain have 18 In the ParlGov research database, party-family average positions on the 0-10 left-right scale are: radical-left = 1.3; green = 2.5; social-democratic = 3.3; agrarian = 5.3; liberal = 6.0;Christian-democratic = 6.A two-bloc system would be more appealing to the British Conservatives than polarised pluralism.A right-wing bloc would include the Tories, Reform UK and Northern Irish unionists.This would entail easier ideological compromises than a grand coalition with Labour.Reform UK would seek to replicate the radical-right's success in Europe.A blocbased party system would give it access to, or influence over, government.A two-bloc system could also work well for Labour.It would look to form governments with the Liberal Democrats and the Greens.It might be possible to exclude a Corbynite party from the Cabinet, on the assumption that it would not join with the right in defeating a centre-left government.Minority cabinets are viable in two-bloc systems if the governing bloc has support parties in parliament.Confidence-and-supply deals with the radical-left party would be possible in return for policy concessions. 19 bloc-based party system could leave the Liberal Democrats in a quandary.Although they might be able to form a 'progressive alliance' with Labour and the Greens, hopes of mobilising some 'latent progressive majority' of voters are misplaced.Simply because a certain percentage of voters back Labour, the Liberal Democrats and Greens combined in a FPTP election does not guarantee they would do so if the parties campaigned in alliance.Under FPTP, the performance of smaller parties is usually endogenous to that of the major parties. 20he Liberal Democrats survive under FPTP because they fulfil a specific role as an anti-Conservative party in constituencies where Labour cannot win.They attract erstwhile Labour supporters, but also ex-Conservatives who would not vote for Labour. 21The latter voters may shun the Liberal Democrats if they joined a centre-left bloc under PR.It is open to question whether space would exist for a leftliberal party, hemmed in by Labour, in a twobloc system.There would be space on the centre-right-but that might not appeal to most Liberal Democrats.
Alternatively, the Liberal Democrats might seek to stand aloof from the blocs, playing kingmakers for left or right.This is risky in a blocbased party system, where voters know they have a choice of left or right governments.An uncommitted centrist party would be inviting voters to abstain from government selection and allow that party to choose the executive itself, after the election.The unfeasibility of this strategy is why small centrist parties in Scandinavia generally align with blocs.
A bloc system could amplify the power of nationalist and unionist parties.A right-bloc government dependent on Northern Irish unionists might be compelled to offer concessions, as with the Conservative-DUP deal in 2017.The SNP would lose its current FPTP seat windfall, but if it kept winning 3-5 per cent of the UK-wide vote under PR, that could translate into 5-10 per cent of the left bloc's seats, a powerful bargaining chip with a Labour-led government.(This charge was levelled at Spain's leftist government of 2019-23, as it relied on Catalan and Basque nationalists for its majority.)It would be hard for the SNP to exercise leverage in a polarised-pluralist system, where its secessionist agenda could see it confined to a cordon sanitaire by the cartel of governing parties.
Are there other reasons for supposing that the British party system under PR would be blocbased rather than polarised-pluralist?The experience of New Zealand, which abandoned FPTP in 1996, may offer some pointers. 22Despite adopting the German electoral system, New Zealand did not develop a German-type party system.Instead, after some flux, it acquired a largely two-bloc system, with Labour and the Greens on the left, and the conservative Nationals and free-market ACT on the right.A small, populist party under a charismatic leader, New Zealand First, has had governing spells with both Labour and National, but it does not always manage to pass the threshold to enter parliament.Grand coalitions, a staple of contemporary polarised pluralism, are anathema to New Zealand.Even after adopting PR, New Zealand retained aspects of the left-right adversarial politics of its majoritarian heritage.Britain under PR would likely do the same.

Conclusion
This article has argued that PR in Britain would fragment the party system, primarily boosting non-centrist parties, with a two-bloc system most likely emerging.How might this affect British debates on electoral reform?The principal virtue claimed for FPTP is voters' ability to select governments.While supporters of FPTP acknowledge its disproportional legislative outcomes, the benefit is governments chosen by voters in elections, not politicians in postelection negotiations.
In two-bloc multiparty systems, however, voters do broadly choose governments.When all parties belong to one of two ideological blocs, voters know that in voting for any given party, they are choosing a governing bloc, as well as an option within that bloc.A voter who voted for Labour or the Greens would be voting for a leftist government.Those supporting the Conservatives or Reform UK would be voting for a right-wing government.
This addresses one of the complaints of PR's critics that voters cannot 'throw the rascals out'.In one respect, a two-bloc system enjoys an accountability advantage over two-partism.In the latter, 'throwing the rascals out' requires crossing the left-right divide and voting for the main opposition party.In a two-bloc system, a voter could do this; alternatively, if she did not wish to cross the left-right divide, she could vote for another party in the same bloc, for example, switching from Labour to the Greens, instead of the Conservatives. 23Accountability is sometimes better achieved by changing the balance within the governing bloc away from the 'rascals', rather than throwing them out entirely.Two-bloc party systems are more likely to produce minority governments than ideologicallyoverlapping ones (they are largely absent, other than in caretaker roles, in Germany, Austria and Benelux).This is partly a consequence of the bloc system anchoring minority governments in a legislative majority, sometimes on a confidenceand-supply basis.This anchor is not available in systems of overlapping coalitions; legislative majorities must be compiled among the governing parties themselves.Not every party in the winning bloc is guaranteed to enter the cabinet, although they may exert influence over policy.The Danish radical-right remained outside centre-right cabinets, but held considerable sway over immigration policy.
Cooperation across the left-right divide is feasible in bloc systems.In Denmark, all parties seek to influence key government policies.Governments seek support across the bloc divide on issues causing tensions in their own bloc.But on the key matter of confidence votes, bloc politics typically rules.Left-right cooperation might need time to establish in Britain, with its majoritarian history.
The prospects of Britain adopting PR look remote at present.The same was once true of Brexit.A hung Parliament, some Liberal-Democrat leverage and the shifting sands of opinion in the Labour Party could precipitate movement.If it does happen, European experience points to a release of latent fragmentation, but with elections continuing to offer voters clear governing choices.
2; conservative = 7.4; radical-right = 8.8; H. Döring and P. Manow, Parliaments and Governments Database (ParlGov), 'Information on parties, elections and cabinets in modern democracies', 2020; www.parlgov.org/TH E B R I T I S H P A R T Y S Y S T E M U N D E R P R O P O R T I O N A L R E P R E S E N T A T I O N 7 © 2023The Authors.The Political Quarterly published by John Wiley & Sons Ltd on behalf of The Political Quarterly Publishing Co.Ltd.The Political Quarterly 1467923x, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/1467-923X.13315by Test, Wiley Online Library on [01/10/2023].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License less to gain from a cordon sanitaire than do liberal and even social-democratic parties.

.3 Contemporary Polarised Pluralism
The Authors.The Political Quarterly published by John Wiley & Sons Ltd on behalf of The Political Quarterly Publishing Co.Ltd.Cabinet formation entails a revolving cast of mainstream parties coalescing to produce majority governments.Alternation is partial, as one or more parties invariably remain in office after each election.This format defines several current day European party systems.Thus, access to government is closed to radical parties, such as Die Linke and AfD in Germany, PVV in the Netherlands and Vlaams Belang in Belgium.
1467923x, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/1467-923X.13315by Test, Wiley Online Library on [01/10/2023].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License restrict access to government, excluding radical parties behind a cordon sanitaire, the system resembles a form of 'contemporary polarised pluralism'.

Table 1 :
Effective number of parliamentary parties in western Europe 14T.Faas and T. Klingelhöfer, 'German politics at the traffic light: new beginnings in the election of 2021', West European Politics, vol.45, no. 7, 2022, pp.1506-21.