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 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.

Africa

Ghana

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.

Zimbabwe

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.

Asia

Lebanon

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.

Australia

House of Representatives

Since the 1920s, the Australian House of Representatives has in effect been a two-party system.
Since the end of World War II, Australia's House of Representatives has been dominated by two factions:
The Coalition has been in government about two-thirds of time, broken by four periods of Labor governments: 1972–1975, 1983–1996, 2007–2013, and since 2022.
The ALP is Australia's largest and oldest continuing political party, formed in 1891 from the Australian labour movement. The party has branches in every state and territory.
The Coalition refers to the alliance between the Liberal Party of Australia and National Party of Australia. It was formed after the 1922 Australian federal election, when the Nationalist Party lost its absolute majority, and was only able to remain in government by allying with the Country Party. Under the Coalition agreement, if the Coalition forms government then the Prime Minister will be the leader of the Liberals, and the Deputy Prime Minister will be the leader of the Nationals. In theory, disagreements between the Coalition's constituent parties would lead to the Coalition splitting apart. This has happened only a few times in Australia's modern political history, and has always resulted in the Coalition coming back together by the next election. The most recent split occurred in 2025, following Labor's landslide victory at that year's election.
One reason for Australia's two-party system is because the House of Representatives is elected through the instant-runoff voting electoral system. Although voters can preference third parties and independents above the major parties, and the voting method has a reduced spoiler effect, there is still only one member per electoral division and so major parties tend to win the vast majority of seats even if they need to rely on preferences to do so. For example, a Labor candidate may win a seat with 30% of the vote for Labor and 21% from Australian Greens voters who ranked Labor second.

Senate

On the other hand, the Australian Senate is effectively a multi-party system, and a Senate majority matching the House is very rare. It uses single transferable vote with multiple Senators for each state/territory. This results in rough proportional representation and as a result, third parties have much more influence and often hold the balance of power. Since 2004, the Australian Greens have been the third largest party in the country, with 8-13% of the national vote and an equivalent amount of Senators. Prior to this, the Australian Democrats was the third largest party. Other current and past parties include One Nation, the Liberal Democrats and Family First.
Some Australian states have seen the rise of minor parties at either the state or federal level, while some have seen long periods of dominance by one party. Some parties are absent entirely in parts of the country.
  • The Australian Capital Territory has had a Labor/Greens coalition government since 2012, opposed by the Liberals. Labor was in government alone from 2001-2012.
  • * Notably, the ACT is the only state/territory where the Greens have been in power.
  • In the Northern Territory, the two main parties are Labor and the Country Liberal Party, which aligns with the Coalition at the federal level.
  • In Western Australia, the Liberal and National parties are not in a permanent coalition at the state level. At the 2021 Western Australian state election Labor won 53 out of 59 lower house seats in a landslide victory. The National Party won 4 seats making them the official opposition. The Liberals won only 2 seats, putting them on the crossbench.
  • In New South Wales and Victoria, the main parties reflect the situation nationally: Labor versus the Coalition of the Liberals and Nationals. NSW is the only state where the Coalition has never split, but has also never merged into one party.
  • In South Australia and Tasmania, the main parties are Labor and the Liberals, with the Nationals not holding any seats.
  • In Queensland, the main parties are Labor and the Liberal-National Party. Historically, the Country Party was the largest Coalition member and they governed the state from 1957 until 1989. This was partially due to a malapportionment which heavily favoured rural seats. It had been originally designed by a Labor government, but ended up benefitting the Country Party as demographics shifted. Later, Premier Joh Bjelke-Petersen increased his power by using Queensland Police to suppress political dissent, and enacted the Bjelkemander, worsening malapportionment in order to reduce the power of the Liberals so his Country Party could rule alone. Eventually, media reports and the Fitzgerald Inquiry revealed wide-ranging corruption police and government. Bjelke-Petersen was forced to resign in disgrace, while many high-ranking police and politicians were criminally charged. Labor has been in power for most of the time since then, with the state Country and Liberal parties merging into the LNP, which is a member of the Coalition federally.

    Europe

Malta

is somewhat unusual in that while the electoral system is single transferable vote, a form with proportional representation traditionally associated with a multi-party system, minor parties have not had much success. Politics is dominated between the centre-left Labour Party and the centre-right Nationalist Party, with no third parties winning seats in Parliament between 1962 and 2017 and since 2022.

Spain

A report in The Christian Science Monitor in 2008 suggested that Spain was moving toward a "greater two-party system" while acknowledging that Spain has many small parties. A 2015 article published by WashingtonPost.com written by academic Fernando Casal Bértoa noted the decline in support for the two main parties, the People's Party and the Spanish Socialist Workers' Party in recent years, with these two parties winning only 52 percent of the votes in that year's regional and local elections. He explained this as being due to the Spanish economic crisis, a series of political corruption scandals and broken campaign promises. He argued that the emergence of the new Citizens and Podemos parties would mean the political system would evolve into a two-bloc system, with an alliance of the PP and Citizens on the right facing a leftist coalition of PSOE, Podemos and the United Left. Far-right Vox party became the third largest group in the Spanish parliament in the late 2010s.

United Kingdom

In countries such as Britain, two major parties which have strong influence emerge and tend to elect most of the candidates, but a multitude of lesser parties exist with varying degrees of influence, and sometimes these lesser parties are able to elect officials who participate in the legislature. In political systems based on the Westminster system, which is a particular style of parliamentary democracy based on the British model and found in many Commonwealth countries, a majority party will form the government and the minority party will form the opposition, and coalitions of lesser parties are possible; in the rare circumstance in which neither party is the majority, a hung parliament arises. Sometimes these systems are described as two-party systems, but they are usually referred to as multi-party systems or a two-party plus system. There is not always a sharp boundary between a two-party system and a multi-party system.
The Labour Party and the Conservative Party are the two largest parties in the United Kingdom since 1922.