What is a primary election?

A primary election is an election in which voters choose their party's nominee for the general election. Primaries are the way most major political parties select candidates for federal, state, and local offices in the United States. Before primary elections became widespread in the early 20th century, party nominees were chosen by party leaders meeting in conventions, often with little input from ordinary voters. Reformers during the Progressive Era pushed to give voters a direct say, leading to the spread of primary elections.

There are two main types of primaries. In a closed primary, only registered members of a party can vote in that party's primary. Republican primary ballots are limited to registered Republicans, and Democratic primary ballots are limited to registered Democrats. Closed primaries are used in states such as New York, Pennsylvania, Florida, and others. In an open primary, any registered voter can vote in either party's primary, regardless of their own party affiliation, though they must choose only one party's primary. Some states use semi-closed primaries, where independents can vote in either party's primary but registered party members can only vote in their own party's primary. A few states use top-two primaries, in which all candidates appear on a single ballot regardless of party, and the top two finishers (regardless of party) advance to the general election. California and Washington use this system.

Presidential primaries are particularly important. Each major party holds presidential primaries (or caucuses) in every state, with delegates allocated based on the results. Iowa traditionally held its caucus first, followed by the New Hampshire primary, though the Democratic Party changed its calendar starting in 2024 to begin with South Carolina. The Democratic and Republican primary calendars run from January or February through June of presidential election years, culminating in the parties' nominating conventions in late summer.

Primary elections matter beyond the immediate question of who wins the nomination. Primaries shape party direction by allowing voters to choose between candidates with different ideological positions and personal styles. They also determine who voters will choose between in the general election. In some states with strong one-party dominance, the primary is effectively the decisive election; in many congressional districts, only one party has a realistic chance in the general election, so the primary determines who serves. Primary turnout is generally lower than general election turnout, and primary voters tend to be more politically engaged and ideologically committed than general election voters.