on in the Australian Senate, which uses a proportional voting system more amenable to minor parties.
India too is showing characteristics of two party system with United Progressive Alliance (UPA) and National Democratic Alliance (NDA) as the two main players. It is to be noted that both UPA and NDA are not two political parties but alliances of several smaller parties. Other smaller parties not aligned with either NDA or UPA exist, and overall command about 20% of the 2009 seats in the Lok Sabha.
Malta are somewhat unusual in that while the electoral system is single transferable vote (STV), traditionally associated with proportional representation, minor parties have not earned much success. No third parties won any seats in the Parliament in Malta's most recent election, for example. The Labour Party and the Nationalist Party are the dominant parties.
Comparisons with other party systems
Two-party systems can be compared with:
- Multi-party systems. In these, the effective number of parties is greater than two but usually fewer than five; in a two-party system, the effective number of parties is two (according to one analysis, the actual average number of parties varies between 1.7 and 2.1.) The parties in a multi-party system can control government separately or as a coalition; in a two-party system, however, coalition governments rarely form. Examples of nations with multi-party systems include Brazil, Canada, Denmark, Finland, France, Germany, India, Pakistan, Indonesia, Ireland, Israel, Italy, Mexico, Nepal, the Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, Taiwan, and the United Kingdom.
- Single-party systems or dominant-party systems happen in nations where no more than one party is codified in law and/or officially recognized, or where alternate parties are restricted by the dominant party which wields power. Examples include rule by the Communist Party of China and the People's Action Party of Singapore.
There are several reasons why, in some systems, two major parties dominate the political landscape. There has been speculation that a two-party system arose in the United States from early political battling between the federalists and anti-federalists in the first few decades after the ratification of the Constitution, according to several views. In addition, there has been more speculation that the winner-takes-all electoral system as well as particular state and federal laws regarding voting procedures helped to cause a two-party system.
Political scientists such as Maurice Duverger and William H. Riker claim that there are strong correlations between voting rules and type of party system. Jeffrey D. Sachs agreed that there was a link between voting arrangements and the effective number of parties. Sachs explained how the First Past The Post voting arrangement tended to promote a two-party system:
The main reason for America's majoritarian character is the electoral system for Congress. Members of Congress are elected in single-member districts according to the "first-past-the-post" (FPTP) principle, meaning that the candidate with the plurality of votes is the winner of the congressional seat. The losing party or parties win no representation at all. The first-past-the-post election tends to produce a small number of major parties, perhaps just two, a principle known in political science as Duverger's Law. Smaller parties are trampled in first-past-the-post elections.—Sachs, The Price of Civilization, 2011
Consider a system in which voters can vote for any candidate from any one of many parties. Suppose further that if a party gets 15% of votes, then that party will win 15% of the seats in the legislature. This is termed proportional representation or more accurately as party-proportional representation. Political scientists speculate that proportional representation leads logically to multi-party systems, since it allows new parties to build a niche in the legislature:
Because even a minor party may still obtain at least a few seats in the legislature, smaller parties have a greater incentiv