Duverger S Hypothesis Statement

Author’s note, November 8, 2016: To remedy potential misunderstandings regarding the implications of this essay, I have written a second piece entitled “Further Gloss on Duverger’s Law: When Third Parties Matter.” As the title suggests, I address when voting for a third party may be a rational decision even absent the prospect of electoral victory. I encourage readers to review both articles.

As the Republican Primary was drawing to a close in April [2012], the Tea Party and its sympathizers alike were naturally disappointed with the results. After GOP voters systematically rejected any and all candidates who even slightly stood by the principles of the Tea Party, some claimed that the Republican Party should be abandoned altogether in favor of a third party candidate. In response, I wrote the following:

A third party movement, they argue, would avoid many of the problems under the current system, instead allowing the Tea Party to stand on nothing more or less than its own principles. To this suggestion, I want to give extreme caution and admonish strongly against it.

America’s political system is not favorable, not even slightly, to third party movements. Throughout the course of US history, there has been not one third party movement which gained enough support to enter a state of prominence in federal politics, and this should be unsurprising. The election laws currently on the books, joined with the (not inaccurate) presupposition of most Americans that third party candidates just cannot win, make for a virtually insurmountable obstacle. In all but few elections, a vote for a third party is nothing more than an act of protest (not that such acts are entirely unjustifiable, just that one should not usually assume that a vote for a third party candidate is likely to push him to victory).”

Since that time, calls for supporting a third party candidate have only grown louder, especially among the supporters of Texas Congressman Ron Paul and former New Mexico Governor Gary Johnson. Whether convinced that they are the victims of a partisan scheme to override the “will of the people” or rationally disenchanted with the status quo candidates offered by both parties, a number of voters are prepared to go to the polls this November and cast their ballot for a third party or independent candidate. My warning remains the same, but it clearly deserves further elaboration.

As it is, there is a sociologist by the name of Dr. Maurice Duverger who has already extensively studied the nature of two-party systems around the world and the lack of electoral viability among third parties in these systems. Not only did he analyze them, but he actually developed his research into a full-fledged law of political science. It is worthy of note that there are few recognized “laws” in any field of social science compared to the natural sciences, primarily due to two key factors of social science – many uncontrollable or immeasurable variables and human agency – which often produce a great number of exceptions to any theory. But later research in Duverger’s theory by other political scientists found so few exceptions that these researchers have elevated it to the status of a political science principle or law. Now, it is only very rarely contested in the political science field.

According to Duverger’s Law, the number of major political parties in any given republican/democratic country is determined by the electoral structure of that country. States with proportional representation – those that award seats to political parties based on the total portion of the popular vote they receive – tend to develop a multi-party system. Single-district plurality voting systems in which seats are allocated district-by-district based on which candidate wins the most votes in that single district – such as the United States – produce a two-party system.

There are two primary reasons for this. The first is that weaker parties will tend to consolidate with one another to improve their chances of winning. The other is that voters themselves tend to gradually desert the weaker parties, instead opting to support (and also influence) their preference in one of the larger parties.

Because only the winner of each district will be granted a seat, parties that consistently come in third place or less will fail to be represented in the government, no matter how much of the vote they receive. This especially disadvantages parties that are spread thin across wide geographic areas. For example, though Ross Perot won 18.9% of the popular vote in 1992, he won no votes in the Electoral College because his supporters were not concentrated enough anywhere to win even a single state. Because of this, only third parties which are geographically concentrated (as they are in Canada, the UK, and India) produce exceptions to Duverger’s Law, and then only to limited success.

Rather than perpetually lose, voters thus consider it more prudent to ally with one of the larger parties. In this way, they can help ensure that the most preferable of the viable choices is elected and that the least preferable is kept out of office. Moreover, participation in one of the larger parties allows voters to influence both the platform and the candidate selection process of that party, something they could not do directly by operating under a third party banner.

In contrast to Duverger’s principle, those currently pushing for a third party split tend to reverse causality. Our electoral system was created and is maintained by America’s two dominant political parties, they claim, not the other way around.

All evidence to the contrary.

America’s electoral system, as outlined by the Constitution, predates the existence of political parties in the United States. At the time of the Constitution’s ratification, the only groups reminiscent of political parties were the Federalists (those in favor of ratifying the Constitution) and the Anti-Federalists (those opposed to ratifying the Constitution). However, neither group was a political party as such. They were factions determined by a single issue, not groups that put candidates forward for election under a partisan platform. A modern example of such factions would be those in favor of legalizing gay marriage and those who are opposed to it, as both groups transcend actual party lines regarding a specific policy position.

In any case, political parties did not develop until later. In fact, George Washington, America’s first president under the Constitution, was not a member of any party, giving him the distinction of being America’s only non-partisan president. Once parties did develop, however, they unsurprisingly did so as a pair: the Federalists (such as John Adams and Alexander Hamilton) and the Democratic-Republicans (such as Thomas Jefferson and James Madison). Since that time, third parties have only risen to power by exploiting the mistakes of one of the two major parties, ultimately replacing the party in error rather than producing a stable three-party system. The vociferously anti-slavery Republican Party, for example, managed to effectively replace the Whig Party in the turmoil preceding the Civil War. With its loose platform, decentralized structure, and failure to address the slavery issue, the Whig Party made itself an easy target for the Republicans. The Federalist Party fell to the Whigs in a similar manner a few decades before.

In sum, America’s two-party system is a result of its electoral structure. Its electoral structure is not a result of its two-party system.

Try as some might to push a third party onto the national political stage, America’s electoral structure is simply an overwhelming obstacle, and this is not necessarily a bad thing. In American governmental bodies, elected figures are intended to represent the interests of their districts first foremost, not the interests of the party or the nation as a whole (the President of the United States being an obvious exception). As such, they are responsive to voters in their districts, knowing well that if they behave in a manner contrary to the will of their district, they can and will be removed from office.  Contrast this with systems of proportional representation where, even if a party’s representation is reduced, the most senior members of that party are safe from electoral accountability. That party would have to lose all its seats for those members to be removed from the government.

“But it isn’t fair!” some complain. “The two-party system only gives us two choices!” Again, this is not the case.

In 2012, there was not one, but rather ten major Republican candidates running for the presidency.  Through the use of primaries (which were not employed until the early twentieth century), GOP voters were able to narrow it down to one. In 2008 across both parties, there were actually twenty-two candidates running for the same office, provided those who dropped out before the Iowa Caucuses are included. And of course, this does not even include the innumerable other candidates one may choose to write-in on the ballot. That one’s personal candidate failed to receive the nomination is not sufficient evidence for anything, especially not a pathology in the system, except that one’s choice was simply not popular (regardless of whether it was rational).

If one’s favorite candidate cannot even win the support of one of the two major parties, what chance does that candidate stand running against both parties? To illustrate this point, examine the results of Ron Paul’s 2012 presidential candidacy: He received 2,095,795 votes out of the 19,242,663 popular votes cast in the Republican primary, or about 10.89%. Using total voter turnout in 2008 as the example (131.3 million), that means that the number of people voting the Republican primary make up about 14.66% of all voters. This means Paul’s supporters in the primary make up about 1.60% of the total electorate, just 0.19% more than the total portion of voters who chose a third party candidate in 2008 (1.41% of the total voting population). Even assuming that he would gain GOP and Democratic defectors in the general election to push that percentage upwards, the results would be the same: the two major parties have their candidates, and one or the other will be chosen. As such, the self-interested choice would be to support the more preferable of the two.

To be completely fair, I did state in April that supporting a third party can serve a valuable political purpose:

Such protests have demonstrated their effectiveness, however. When a third party draws enough votes away from the usual constituents of one of the larger parties, the slighted party attempts to integrate the dissenters into its membership.  Take, for instance, the various presidential runs made by Eugene V. Debs in the early Twentieth Century on behalf of the Socialist Party. Naturally, the Democrats suffered a loss in support, and systematically altered their platform to be more agreeable to the supporters of the Socialist Party – the result was Woodrow Wilson. The same applies to the Republican Party as affected by the Progressive Party run made by Theodore Roosevelt in 1912. The eventual, though slower, result of such a shift was Herbert Hoover.

I stand by that statement. Were the political conditions right, a third party defect could prove rationally self-interested in the long run by compelling one of the major parties to accommodate increasingly laissez-faire positions. Unfortunately, there is hardly a “long run” left to speak of.

It is odd that, for a group whose preferred candidate spoke so passionately (and rationally) about America’s impending monetary and economic collapse, Ron Paul supporters often appear the least concerned about having a nihilist occupy (no pun intended) the Oval Office for two terms in a row. If this collapse is as imminent as Paul suggests (and it is), then the rationally self-interested thing to do when no solution is present is to buy more time until a solution can be achieved. And make no mistake, Mitt Romney is certainly no solution. He is contemptible and a statist, but not a nihilist. Thus, he is the preferable, self-interested option in the 2012 presidential cycle. Specific reasons why this is so need not be discussed here; Dr. Leonard Peikoff has already offered a stellar explanation of why it is rationally selfish to vote for Mitt Romney in 2012. Rather, the perspective here is one of political science and legal theory, analyzing in non-moral terms why voting for a third party in the United States is, more often than not, a fruitless endeavor.

Instead, capitalists should work within the existing political structure rather than attempt to overcome it. Surely, such efforts have made progress over the last few years – one need only note the GOP’s “audit the Fed” addition to its platform and the slight uptick in “pro-businessman” rhetoric at the convention to be aware of that.

…[W]hy try to affect the platform of a party externally when one is already inside said party? Rather than sit and listen to the nonsense about the ‘Establishment’ having coopted their own movement, Tea Partiers should actively engage in trying to coopt the Republican Party. Again, the Republican Party lacks a clearly defined philosophy – a philosophy which the Tea Party could potentially give it. Through the continued involvement in the lower rungs of the Republican Party, Tea Partiers have the opportunity to change the Republican Party from the ground up, converting the other Republicans or, at the very least, getting them to toe a new partisan line.

This should be the goal of capitalists and other free-market-leaning individuals: facilitate and contribute to a cultural change in favor of capitalism, unwaveringly advocate the philosophic substructure which supports it, and reform the Republican Party rather than abandon it. Morally, it is the rational course to take – politically, the only viable one.

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Written by Brian Underwood

Brian has worked as a clerk in the Georgia State Senate, and is currently enrolled in the Duke University School of Law as a JD candidate for 2017. Brian holds degrees in Political Science and History from the University of Georgia.

In political science, Duverger's law holds that plurality-rule elections (such as first past the post) structured within single-member districts tend to favor a two-party system, whereas "the double ballot majority system and proportional representation tend to favor multipartism".[1][2] The discovery of this tendency is attributed to Maurice Duverger, a French sociologist who observed the effect and recorded it in several papers published in the 1950s and 1960s. In the course of further research, other political scientists began calling the effect a "law" or principle.

Duverger's law draws from a model of causality from electoral system to a party system. A proportional representation (PR) system creates electoral conditions that foster development of many parties, whereas a plurality system marginalizes smaller political parties, generally resulting in a two-party system.

In practice, most countries with plurality voting have more than two parties. While the United States is very much a two-party system, the United Kingdom, Canada and India have consistently had multiparty parliaments.[3][4] Eric Dickson and Ken Scheve argue that there is a counter force to Duverger's Law, that on the national level a plurality system encourages two parties, but in the individual constituencies supermajorities will lead to the vote fracturing.[5]Steven R. Reed has shown Duverger's Law to work in Japan[6] and Italy;[7] the "extension of Duverger's Law into Japanese case", as Gary W. Cox notes, resulting in Reed's identification of the M + 1 equilibrium.[8]


A two-party system often develops in a plurality voting system. In this system, voters have a single vote, which they can cast for a single candidate in their district, in which only one legislative seat is available. In plurality voting (i.e. first past the post), in which the winner of the seat is determined purely by the candidate with the most votes, several characteristics can serve to discourage the development of third parties and reward the two major parties.

Duverger laid out two paths by which plurality voting systems lead to fewer major parties: the "fusion" or alliance of weaker parties into more effective factions, and the "elimination" of weak parties as voters gradually desert them because they have no chance of winning and influencing governance.[9][10]

Because the system gives only the winner in each district a seat, a party which consistently comes in second or third in every district will not gain any seats in the legislature, even if it receives a large minority of the vote. This puts geographically thinly spread parties at a significant disadvantage to geographically concentrated ones with the same overall level of public support. An example of this is the Liberal Democrats in the United Kingdom, whose proportion of seats in the legislature is significantly less than their proportion of the national vote. The Green Party of Canada is also a good example. The party received about 5% of the popular vote from 2004 to 2011 but had only won one seat (out of 308) in the House of Commons in the same span of time. Another example was seen in the 1992 U.S. presidential election, when Ross Perot's candidacy received zero electoral votes despite getting 19% of the popular vote. Gerrymandering is sometimes used to counteract such geographic difficulties in local politics but is controversial on a large scale. These numerical disadvantages can create an artificial limit on the level at which a third party can engage in the political process.

The second unique problem is both statistical and tactical. Duverger suggested an election in which 100,000 moderate voters and 80,000 radical voters are voting for a single official. If two moderate parties ran candidates and one radical candidate were to run, the radical candidate would win unless one of the moderate candidates gathered fewer than 20,000 votes. Observing this, moderate voters would be more likely to vote for the candidate most likely to gain more votes, with the goal of defeating the radical candidate. Either the two parties must merge, or one moderate party must fail, as the voters gravitate to the two strong parties, a trend Duverger called polarization.[11]

A third party can enter the arena only if it can exploit the mistakes of a pre-existing major party, ultimately at that party's expense. For example, the political chaos in the United States immediately preceding the Civil War allowed the Republican Party to replace the Whig Party as the progressive half of the American political landscape. Loosely united on a platform of country-wide economic reform and federally funded industrialization, the decentralized Whig leadership failed to take a decisive stance on the slavery issue, effectively splitting the party along the Mason–Dixon line. Southern rural planters, initially attracted by the prospect of federal infrastructure and schools, aligned with the pro-slavery Democrats, while urban laborers and professionals in the northern states, threatened by the sudden shift in political and economic power and losing faith in the failing Whig candidates, flocked to the increasingly vocal anti-slavery Republican Party.

In countries that use proportional representation (PR), a two-party system is less likely, especially in countries where the whole country forms a single constituency, as it does in Israel, along with low electoral thresholds to obtain office. Israel's electoral rules historically had an electoral threshold for a party to obtain a seat as low as one-percent of the vote; the threshold is 3.25% as of 2014. Germany's threshold in its Bundestag is either 5% of the national party vote or three (directly elected) constituency representatives for a party to gain additional representation through proportional representation. The number of votes received for a party determines the number of seats won, and new parties can thus develop an immediate electoral niche. Duverger identified that the use of PR would make a two-party system less likely. However, other systems do not guarantee new parties access to the system: Malta provides an example of a stable two-party system using the single transferable vote, although it is worth noting that its presidential elections are won by a plurality, which may put a greater two-party bias in the system than in a purely proportional system.


Duverger did not regard this principle as absolute, suggesting instead that plurality would act to delay the emergence of new political forces and would accelerate the elimination of weakening ones,[11] whereas proportional representation would have the opposite effect. The following examples are partly due to the effect of smaller parties that have the majority of their support concentrated in a small number of electorates rather than diluted across many electorates. William H. Riker noted that strong regional parties can distort matters, leading to more than two parties receiving seats in the national legislature, even if there are only two parties competitive in any single district.

The following example seems counter to the law:

There are also cases where the principle appears to have an effect, but weakly:

  • In India, there are 38 political parties represented in the Parliament. Like the UK and Canada, India has a winner-takes-all system.[12] Most of the Indian parties are allied with one of two larger electoral coalitions which makes the Indian system functionally somewhat like a two-party system.
  • In Canada, five parties are represented in the House of Commons, and the number has averaged between 4 and 5 since 1935. Only three of these (governing Liberals, opposition Conservatives and third place NDP) are considered "major parties" because the other two parties lack official party status as they hold fewer than 12 seats. Canada has had more than two registered parties in the House of Commons, since 1921, and at only three relatively brief periods in Canadian history have there been only three parties represented (1921–1935, 1958–1962, and 1980–1993).
  • In the United Kingdom, the SDP–Liberal Alliance, and later Liberal Democrats, have, since the February 1974 General Election, obtained 1–10% of seats forming a third party, albeit with significantly fewer seats.[13] This share of seats is despite gathering around a fifth of votes consistently over the same time period.[14] In the UK there is no president and thus no unifying election to force party mergers and regional two party systems are formed. This is because Duverger's law says that the number of viable parties is one plus the number of seats in a constituency. In Scotland, Labour and the SNP have been the two dominant parties (the Scottish Conservatives have experienced a resurgence in the 2017 General Election and Scottish Elections[15][16]). The SNP has replaced the Lib Dems in this role. In southwest England, the Lib Dems face off against the Conservatives. Labour voters may vote for the Lib Dems to prevent a Conservative from winning. Caroline Lucas of the Green Party has held a seat since 2010.

Other parties have won seats[when?], but they are either elected outside England, where the British FPTP system is used in parallel to the Welsh and Scottish proportional-representation multiparty democracy, or through by-elections (such as the Respect Coalition). Northern Ireland has an entirely separate political system in which neither Labour nor the Liberal Democrats stand candidates, the Conservatives occasionally do but are not competitive.

Riker pointed to Canada's regional politics, as well as the U.S. presidential election of 1860, as examples of often temporary regional instability that occurs from time-to-time in otherwise stable two-party systems (Riker, 1982). In the case of Canada, the highly regionalised parties are evident in province-by-province examination: while the multiparty system can be seen in the Canadian House of Commons, many of the provinces' elections are dominated by two-party systems. Quebec, for instance, is driven mainly by the sovereigntist, center-left Parti Québécois and the center-right Liberal Party, while in Saskatchewan, it is the left-wing New Democratic Party and the centre-right Saskatchewan Party (a coalition of those affiliated with the Conservative and Liberal Parties). Unlike in the United States, where the two major parties are organized and unified at the federal, state and local level, Canada's federal and provincial parties generally operate as separate organizations.


Two-party politics may emerge in systems that do not use the plurality vote,[17] especially in countries using systems that do not fully incorporate proportional representation. For instance, Malta has a single transferable vote (STV) system and apparently stable two-party politics.

Some systems are even more likely to lead to a two-party outcome: for example, elections in Gibraltar use a partial block vote system (which is classified as majoritarian) in a single constituency, so the third most popular party is unlikely to win any seats.

In recent years some researchers have modified Duverger's Law by suggesting that electoral systems are an effect of party systems rather than a cause.[18] It has been shown that changes from a plurality system to a proportional system are typically preceded by the emergence of more than two effective parties, and are typically not followed by a substantial increase in the effective number of parties.[19]

See also[edit]


  1. ^Grzymala-Busse, Anna (31 December 2014). "Remembering Duverger". Mischiefs of Faction. 
  2. ^Sartori, Giovanni (1994). Comparative Constitutional Engineering: An Inquiry into Structures, Incentives and Outcomes. Macmillan. 
  3. ^Dunleavy, Patrick (18 June 2012). "Duverger's Law is a dead parrot. Outside the USA, first-past-the-post voting has no tendency at all to produce two party politics". blogs.lse.ac.uk. 
  4. ^Dunleavy, Patrick; Diwakar, Rekha (2013). "Analysing multiparty competition in plurality rule elections"(PDF). Party Politics. 19 (6): 855–886. doi:10.1177/1354068811411026. 
  5. ^Dickson, Eric S.; Scheve, Kenneth (2010). "Social Identity, Electoral Institutions and the Number of Candidates"(PDF). British Journal of Political Science. 40 (2): 349–375. doi:10.1017/s0007123409990354. JSTOR 40649446. 
  6. ^Reed, Steven R. (1990). "Structure and Behaviour: Extending Duverger's Law to the Japanese Case". British Journal of Political Science. 20 (3): 335–356. doi:10.1017/S0007123400005871. JSTOR 193914. 
  7. ^Reed, Steven R. (2010). "Duverger's Law is Working in Italy". Comparative Political Studies. 34 (3): 312–327. doi:10.1177/0010414001034003004. 
  8. ^Gary W. Cox, Making Votes Count (Cambridge University Press, 1997)
  9. ^Schlesinger, Joseph A.; Schlesinger, Mildred S. (2006). "Maurice Duverger and the Study of Political Parties"(PDF). French Politics. 4: 58–68. doi:10.1057/palgrave.fp.8200085. Archived from the original(PDF) on 24 July 2011. Retrieved 2011-12-17. 
  10. ^Wada, Junichiro (2004-01-14). The Japanese Election System: Three Analytical Perspectives. ISBN 9780203208595. 
  11. ^ abDuverger, Maurice (1972). "Factors in a Two-Party and Multiparty System". Party Politics and Pressure Groups. New York: Thomas Y. Crowell. pp. 23–32. 
  12. ^Lok Sabha ({Dead link |date=Dec 2017}}
  13. ^See references in United Kingdom general elections, 1974 to 2010.
  14. ^Liberal Democrats#Electoral results
  15. ^"Results of the 2017 General Election". BBC News. Retrieved 2018-01-29. 
  16. ^Sim, Philip (2017-06-12). "Scotland's election results in numbers". BBC News. Retrieved 2018-01-29. 
  17. ^Cox, Gary W. Making Votes Count: Strategic Voting in the World's Electoral Systems. San Diego, CA: University of San Diego Press, 1997.
  18. ^Benoit, Kenneth (2007). "Electoral Laws as Political Consequences: Explaining the Origins and Change of Electoral Institutions". Annual Review of Political Science. 10 (1): 363–390. doi:10.1146/annurev.polisci.10.072805.101608. 
  19. ^Colomer, Josep M. (2005). "It's Parties that Choose Electoral Systems (or Duverger's Law Upside Down)"(PDF). Political Studies. 53 (1): 1–21. doi:10.1111/j.1467-9248.2005.00514.x. Archived from the original(PDF) on 3 February 2006. Retrieved 2009-05-31. 


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