Two-party system
A two-party system is a party system where two major political parties dominate the government. 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 has different senses. For example, in the United States, Jamaica, and Malta, the sense of "two-party system" describes an arrangement in which all or nearly all elected officials belong to one of the only two major parties, and third parties rarely win any seats in the legislature. In such arrangements, two-party systems are thought to result from various factors like winner-takes-all election rules. In such systems, while chances for third-party candidates winning election to major national office are remote, it is possible for groups within the larger parties, or in opposition to one or both of them, to exert influence on the two major parties. In contrast, in the United Kingdom and Australia and in other parliamentary systems and elsewhere, the term "two-party system" is sometimes used to indicate an arrangement in which two major parties dominate elections but in which there are viable third parties which do win seats in the legislature, and in which the two major parties exert proportionately greater influence than their percentage of votes would suggest.
Political party
French political scientist Maurice Duverger drew a distinction between "cadre" parties and "mass" parties. Cadre parties were political elites that were concerned with contesting elections and restricted the influence of outsiders, who were only required to assist in election campaigns. Mass parties tried to recruit new members who were a source of party income and were often expected to spread party ideology as well as assist in elections. Socialist parties are examples of mass parties, while the Conservative Party in the UK and the German Christian Democratic Union in Germany are examples of hybrid parties. In the United States, where both major parties were cadre parties, the introduction of primaries and other reforms has transformed them so that power is held by activists who compete over influence and nomination of candidates.