American electoral politics have been dominated by successive pairs of major political parties since shortly after the founding of the republic of the United States. Since the 1850s, the two largest political parties have been the Democratic Party and the Republican Party—which together have won every United States presidential election since 1852 and controlled the United States Congress since at least 1856. Despite keeping the same names, the two parties have evolved in terms of ideologies, positions, and support bases over their long lifespans, in response to social, cultural, and economic developmentsthe Democratic Party being the left-of-center party since the time of the New Deal, and the Republican Party now being the right-of-center party.
Political parties are not mentioned in the U.S. Constitution (which predates the party system). The two-party system is based on laws, party rules, and custom. Several third parties also operate in the U.S. and, from time to time, elect someone to local office. Some of the larger ones include the Constitution, Green, Alliance, and Libertarian parties, with the latter being the largest third party since the 1980s. A small number of members of the US Congress, a larger number of political candidates, and a good many voters (35-45%) have no party affiliation. However, most self-described independents consistently support one of the two major parties when it comes time to vote, and members of Congress with no political party affiliation caucus meet to pursue common legislative objectives with either the Democrats or Republicans.
The need to win popular support in a republic led to the American invention of voter-based political parties in the 1790s. Americans were especially innovative in devising new campaign techniques that linked public opinion with public policy through the party. Political scientists and historians have divided the development of America's two-party system into six or so eras or "party systems", starting with the Federalist Party, which supported the ratification of the Constitution, and the Democratic-Republican Party or the Anti-Administration party (Anti-Federalists), which opposed a powerful central government.
History and political eras
Founding fathers
The United States Constitution is silent on the subject of political parties. The Founding Fathers did not originally intend for American politics to be partisan. In Federalist Papers No. 9 and No. 10, Alexander Hamilton and James Madison, respectively, wrote specifically about the dangers of domestic political factions. In addition, the first President of the United States, George Washington, was not a member of any political party at the time of his election or throughout his tenure as president. Furthermore, he hoped that political parties would not be formed, fearing conflict and stagnation, as outlined in his Farewell Address. The Founders "did not believe in parties as such, scorned those that they were conscious of as historical models, had a keen terror of party spirit and its evil consequences," but, Richard Hofstadter wrote, "almost as soon as their national government was in operation, [they] found it necessary to establish parties."
In the past 150-plus years the two dominant parties have changed their ideologies and bases of support considerably, while maintaining their names. In the aftermath of the Civil War, the Democratic party was an agrarian pro-states-rights, anti-civil rights, pro-easy money, anti-tariff, anti-bank, coalition of Jim Crow Solid South and Western small farmers. Budding labor unions and Catholic immigrants were the dominant participants in the Democratic party of the time. As of 2020, the Democratic party has become a strongly pro-civil rights party, disproportionately composed of women, LGBT people, union members, and urban, educated, younger, non-white voters. During the same period, following the Civil War, the Republican party was the dominant American "Grand Old Party" of businesses large and small, skilled craftsmen, clerks, professionals, and freed African Americans, based especially in the industrial northeast. In modern society, the Republican party has become a right-wing party, disproportionately composed of family businesses, older, rural, southern, religious, and white working class voters. Along with this realignment, political and ideological polarization has increased, and norms have deteriorated, leading to greater tension and "deadlocks" in attempts to pass ideologically controversial bills.