A political party in a democracy is an independent and freely formed organization that nominates candidates for positions in government with the purpose of winning elections in order to form or control the government. Competition between candidates and political factions or parties is an essential characteristic of a genuine constitutional democracy. If only one political party is permitted to function in a country, or if there is only one officially approved slate of candidates, then there is not a democracy.
During the period between elections in a democratic country, the political parties that failed to win control of the government are free to criticize or otherwise legally oppose the ideas of the ruling party or coalition of parties. Thus, they try to win support among voters that will enable them to win the next election. If opposition to the ruling party is silenced, then there is not a democracy.
In a few democracies, such as Great Britain and the United States of America, there are only two major political parties that compete to win control of the national government. In the United States, for example, there are the Democrats and the Republicans, and in Great Britain, the Conservative Party and the Labour Party.
Minor parties may exist in a two-party system, but rarely does one or more of their candidates win a position in national government. From time to time, however,a major party will adopt ideas put forward by a minor party. Sometimes a minor party grows strong enough to replace one of the major parties in a two-party system. During the 20th century, for example, the Labour Party in Great Britain was a minor party that grew strong enough to replace the Liberal Party as one of the two major parties.
In most democracies, there is a multiple-party system; there are several major political parties whose candidates have a realistic chance to win election to the government, and there are many other minor parties that rarely if ever win representation in the government. For example, there are at least eight political parties that usually win seats in the parliament of Estonia. But Estonia also has more than 30 minor parties that typically do not attract enough voters to be represented at all in the parliament. Nonetheless, they are free to express their ideas in the continuing hope of winning greater support among the voters.
Multiple political party systems prevail in parliamentary democracies that use proportional representation. Under proportional representation, the members of parliament do not represent constituents in a particular district of the country. Instead, candidates run for office as members of their political party’s slate or list of candidates, which represent the country as a whole and not a single constituency. Thus, voters cast their ballots for one party’s list of candidates in preference to the lists of competing political parties.
The number of seats that a party wins in the parliament is based on the percentage of votes cast for the party’s list of candidates. For example, suppose there are one hundred members of the parliament. A political party that wins 16 percent of the votes will have 16 members in the parliament; another party that wins 25 percent of the votes will have 25 members of the legislative body.
In electoral systems based on proportional representation, there is usually a rule that in order to win at least one seat in the parliament, a party must win at least 5 percent of the total votes cast in the election. Thus, political parties with very little support cannot hope to be represented in the parliament. This rule enhances the possibility that one party or a coalition of only two or three parties will gain the majority of seats in the parliament necessary to form a government.
Two-party systems prevail in democracies with an electoral system based on single-representative districts, such as in the United States, Great Britain, and some other countries founded and formerly ruled by Britain, such as Australia, Canada, and New Zealand. The candidate for the legislative body (in Britain the House of Commons, in the U.S. the Congress) with a majority or plurality of votes cast in each electoral district wins the seat for that district. This system discourages multiple political parties from competing in the single-representative districts upon which the election is based because only the candidate with the most votes wins a seat in the legislature and the losing party or parties get no seats, as might be the case in the proportional representation system.
Some multiple-party democracies have an electoral system that is a mixture of two electoral systems: the proportional representation system and the single-representative district system. In all genuine democracies, more than one political party has the constitutional right to compete periodically in elections in order to form and conduct the government. However, if genuine democracy would prevail, the winners of majority support among the people must respect equally and fairly the rights of parties in the minority. – John Patrick, Understanding Democracy, A Hip Pocket Guide