Two-party system

A two-party system is a political party system in which two major political parties consistently dominate the political landscape. At any point in time, one of the two parties typically holds a majority in the legislature and is usually referred to as the majority or governing party while the other is the minority or opposition party. Around the world, the term is used to refer to one of two kinds of party systems. Both result from Duverger's law, which demonstrates that "winner-take-all" or "first-past-the-post" elections produce two dominant parties over time.

The first type of two-party system is an arrangement in which all (or nearly all) elected officials belong to one of two major parties. In such systems, minor or third parties rarely win any seats in the legislature. Such systems exist, for example, in the United States, the Bahamas, Jamaica, and Zimbabwe. In such systems, while chances for third-party candidates winning election to major national office are remote, it is possible for factions within the larger parties to exert influence on one or even both of the two major parties.

Two-party system also indicates an arrangement, common in parliamentary systems, in which two major parties dominate elections, but in which there are viable minor parties and/or independents regularly elected to the legislature. These successful minor parties are often regional parties. In these systems, the two major parties exert proportionately greater influence than their percentage of voters would suggest, and other parties may frequently win election to local or subnational office. Canada, the United Kingdom, and Australia are examples of countries that have this kind of two-party system.

The Republic of Ghana since its transition to democracy in 1992 have a strongly institutionalized two-party system led by New Patriotic Party and National Democratic Congress.

The politics of Zimbabwe are effectively a two-party system between the Robert Mugabe founded Zimbabwe African National Union-Patriotic Front and the opposition coalition Movement for Democratic Change.

The Parliament of Lebanon is mainly made up of two bipartisan alliances. Although both alliances are made up of several political parties on both ends of the political spectrum the two-way political situation has mainly arisen due to strong ideological differences in the electorate. Once again this can mainly be attributed to the winner takes all thesis.

South Korea has a multi-party system that has sometimes been described as having characteristics of a two-party system. Parties will have reconstructions based upon its leader, but the country continues to maintain two major parties. Currently these parties are the liberal Democratic Party of Korea and the conservative People Power Party.

Since the 1920s, the Australian House of Representatives (and thus the federal government) has in effect been a two-party system.