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Definition: two-party system from The Macquarie Dictionary

a system of government in which two major political parties, more or less equal in strength, contend for election to power.

Summary Article: Two-Party System
From Encyclopedia of U.S. Campaigns, Elections, and Electoral Behavior

A TWO-PARTY SYSTEM is found in democracies such as Great Britain and the United States, where only two parties gain the vast majority of votes and offices at all levels of government. Two-party systems are rare outside Great Britain and former British colonies; they are typically associated with a relatively simple cleavage structure and single-member district plurality elections.

Proponents praise the simplicity of such a system, arguing that it ensures governmental stability, it indicates clearly where responsibility lies, and has a moderating influence over the main political actors. In a parliamentary system, in addition to making the choice easier for voters, the two-party system is considered more democratic because it gives voters an opportunity to choose the government, unlike multiparty systems where government is the result of post-election negotiations among party leaders. Critics say that a two-party system limits representation and the range of policies considered for enactment.

There is more than one kind of two-party system; British two-partyism is very different from the American two-partyism. The institutional context is crucial for how a two-party system actually works and for its effects on policymaking. The key distinction here is between America’s presidential system and Britain’s parliamentary system. Although the logic of a two-party system is inherently majoritarian, the existence of separation of powers opens the door for divided government. This can mitigate the winner-takes-all effect of the two-party system when, as it is often the case in the United States, one party is in control of Congress and the other party controls the White House. The British parliamentary system, with its fusion of legislative and executive powers, prevents such an occurrence. In a parliamentary regime, a two-party system means that the party that has a majority in the legislature is also forming the government. Such single-party governments have a higher life expectancy than multiparty governments.

Party discipline is another important difference between the British and the American two-party system, and is largely a result of the different institutional incentives provided by presidentialism and parliamentarism. In Britain, the prime minister is also the leader of the legislative majority, and therefore has the means to ensure the compliance of the rank-and-file members of parliament representing the majority party. Parties select the candidates for office, as in other European nations. British parties are centralized and disciplined, and representatives from the same party tend to vote as a bloc. Those who follow the party line enhance their chances for being rewarded in the future with a better position in the government, and party dissidence is rare.

American parties are decentralized and undisciplined; party dissent is more common than in Britain. Thus, unlike the impact of parliamentarism in Britain, which maintains the cohesiveness of the two major parties, American-style presidentialism has somewhat contradictory effects on the party system. It reinforces the existing two-party system, as only the two major parties have a chance to capture the most important office, but it weakens the two parties, because it lacks the additional incentive (the fusion between legislative and executive power) that makes their British counterparts so disciplined and cohesive. Finally, having the candidates for office selected through primary elections, rather than party organizations, as in Britain, further enhances the independence of office holders.

Equally important in accounting for the differences between American and British two-partyism are the differences between the two societies. America is much larger than Britain, in geography and population, and significantly more diverse. The consequence of this is that American legislators from the same party represent constituencies that are more diverse than British members of parliament from the same party and this, in turn, makes American parties more divided internally than their British counterparts.

Two arguments in favor of two-partyism are the argument that a two-party system has a moderating influence, and that the existence of only two parties offers voters a clear choice. Because the truth of either claim makes the other less plausible, proponents tend to focus on only one or the other. Typically, the first argument was advanced in the American context, and the second claim in the British context.

During the 1970s and 1980s, there were dramatic shifts in policies whenever there was a transition from a Labour government to a Conservative government and vice versa, with Labour nationalizing major industries which were then returned to private owners by Conservatives. During the same time, the ideological distance between America’s major parties appeared comparatively narrow. Thus, depending on the country, either claim could be confirmed empirically.

In recent years, though, things appear to have changed in both countries. In Britain, Labour’s success in is largely due to the party’s adoption of moderate policy positions. Currently, British politics is less polarized than in the 1980s. At the same time, there is a widening policy gap between the positions endorsed by the Republicans and the Democrats in the United States. America’s diversity as a society is not mirrored at the constituency level; an increasing number of representatives are elected either from rural (or suburban), predominantly white, conservative districts, or from urban, minority-dominated, liberal districts. There is an increasing heterogeneity across districts, but an increasing homogeneity within districts. The result is that the ideological distance separating the two parties is currently greater than it was at any point in the last 50 years.

Although two-party systems tend to be associated with single-member district plurality elections, plurality is neither necessary, nor sufficient for the existence of a two-party system. There are examples of countries such as Malta and, until the 1980s, Austria that maintained a two-party system for a long time, in spite of using proportional representation. There are also examples of countries such as Canada or India that have multiparty systems, even though they use plurality elections.

  • Multiparty System; Plurality Vote; Realignment.

  • Jean BlondelParty Systems and Patterns of Government in Western Democracies,” Canadian Journal of Political Science (v.1/2, 1968).
  • Maurice Duverger, “Party Systems,” in Party Politics and Pressure Groups (Thomas Y. Crowell, 1972).
  • T. J. Lowi; Joseph Romance, A Republic of Parties’? Debating the Two-Party System (Rowman & Littlefield, 1998).
  • Florin Fesnic
    University of Bucharest
    Copyright © 2008 by SAGE Publications, Inc.

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