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In nations that have two or more parties, each party selects candidates for the various public offices. The voters then decide which candidates among the parties win office. Party leaders try to select candidates who have voter appeal and experience for the office. .
During the early history of the United States, party leaders selected candidates for office in meetings called caucuses. But the caucus system became unpopular because it gave other party members little voice in the selection of candidates. In addition, one person or a small group of persons sometimes gained control of a caucus and used it for private gain. See Caucus. .
By about 1840, the convention system for nominating candidates was in general use. Under this system, party members chose delegates to represent them at nominating conventions. But party bosses and political machines (organizations within a party) gained control of many conventions. Many delegates voted the way they were told or paid to vote. Today, conventions are held in only a few states to make some nominations for state and local offices and to discuss party affairs. The two major U.S. political parties "the Democratic and Republican parties "still hold a national convention every four years to officially nominate candidates for president and vice president. See Political convention. .
During the early 1900's, many states began to replace the convention system with primary elections to select candidates for office. The aim was to reduce party control in the selection of candidates. Today, all states hold either open or closed primary elections for state offices. In an open primary, each voter receives the ballots of all parties holding primaries. In the voting booth, the voter selects which ballot to use. In a closed primary, voters receive only the ballot of the party to which they belong. In recent years, the Republican and Democratic parties have relied on primary elections "and, in some states, caucuses "to select their presidential candidates.