Political parties are groups of individuals organized for the purpose of electing candidates to public office. The Constitution contains no mention of parties, and the Framers regarded them as undesirable or even dangerous. Nonetheless, the federal structure and electoral institutions they created give ample incentives for party building.

The first American parties formed during the first few decades of the Republic as congressional members attempted to build stable coalitions to control the machinery of government. These attempts quickly spilled over into the electoral arena. With the plurality voting rule penalizing all but a few serious candidates for each office, the two-party pattern of electoral competition quickly emerged. Two-party competition lapsed briefly during the Era of Good Feelings, but revived following the 1824 presidential election and has endured without interruption ever since.

In the nineteenth century, many state and local parties could be classified as party machines—hierarchical organizations controlled by a single boss. Party machines operated under an exchange relationship: politicians provided favors and services to people in exchange for continued electoral support. During the Progressive Era, reforms were implemented to weaken machine rule. The most important of these were civil service laws, the Australian ballot, and primary elections.

Diverse party alliances formed during the New Deal helped illustrate the coalitional nature of American politics. As new issues emerged, these coalitions began to unravel. Trends such as increased indifference to the parties, growing vote shares won by independents and third-party candidates, and divided control of government suggested parties were on the decline. However, the Democratic and Republican Parties continue to dominate electoral politics, and partisanship has resurged among voters over the past two decades.

While the characteristics and strength of American political parties have changed over time, they continue to perform vital functions in our system of government. Parties recruit and train political leaders, organize the activities of government, and facilitate the collective action needed to translate voter preferences into public policies. For voters, they provide useful cues and mechanisms for holding elected officials accountable. Thus, despite the disdain that many citizens and politicians profess for them, their usefulness ensures that political parties will continue to thrive.