Political parties serve to link the public with its elected leaders. In the United States this linkage is provided by a two-party system; only the Republican and Democratic parties have any chance of winning control of government. The reality that the United States has only two major parties is explained by several factors, including an electoral system characterized by single-member districts which makes it difficult for third parties to compete for power. Also, each party accepts a variety of different political views, and the parties exist in a political culture that stresses compromise and negotiation rather than ideological rigidity.
Because the United States has only two major parties, each of which seeks to gain majority support, their candidates normally tend to avoid controversial or extreme political positions. Candidates typically pursue moderate and somewhat overlapping policies. Nonetheless, the Democratic and Republican candidates sometimes do offer sharply contrasting policy alternatives, particularly in times of political unrest.
America's parties are decentralized, fragmented organizations. The national party organization does not control the policies and activities of the state organizations, and they in turn do not control the local organizations. Traditionally the local organizations have controlled most of the party's work force because most elections are contested at the local level. Local parties, however, vary markedly in their vitality. Whatever their level, America's party organizations are relatively weak. They lack control over nominations and elections. Candidates can bypass the party organization and win nomination through primary elections. Individual candidates also control most of the organizational structure and money necessary to win elections. Recently the state and national party organizations have expanded their capacity to provide candidates with modern campaign services. Nevertheless, party organizations at all levels have few ways of controlling the candidates who run under their banner. They assist candidates with campaign technology, workers and funds but cannot compel candidates' loyalty to organizational goals.
American political campaigns, particularly those for higher-level office, are candidate-centered. Most candidates are self-starters who become adept at "the election game." They spend much of their time raising campaign funds and build their personal organizations around "hired guns": pollsters, media producers and election consultants. Strategy and image-making are key components of modern campaigns, as is televised political advertising, which accounts for roughly half of all spending in presidential and congressional races.
Because America's parties cannot control their candidates or coordinate their policies at all levels, they are unable to consistently present voters with a coherent, detailed platform for governing. The national electorate as a whole is thus denied a clear choice among policy alternatives and has difficulty exerting a decisive and predictable influence through elections.