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Elections

Primary election

A primary election is an electoral process in which voters select the candidates who will represent a political party in a subsequent general election. Primaries are used in many countries, but they are most prominent in the United States, where they determine the nominees for offices ranging from local councils to the presidency. The rules governing primaries vary widely by state and party, including open, closed, and semi-closed systems, and they have evolved over time to shape party politics and voter participation.

1842
First statewide primary law (Wisconsin)
Year
~50
U.S. states and territories holding primaries
Count
2024
Most recent U.S. presidential primary cycle
Year
1

Types and rules

Primary elections are classified by who may vote. In a closed primary, only registered party members may vote for that party's nominee; in an open primary, any voter may participate regardless of party affiliation. Semi-closed primaries allow unaffiliated voters to choose one party's ballot, while semi-open primaries permit voters to switch parties on election day. A blanket primary (now largely unconstitutional after the 2000 U.S. Supreme Court case California Democratic Party v. Jones) listed all candidates on one ballot, with the top vote-getter from each party advancing. Top-two and top-four primaries, used in states like California and Alaska, send the leading candidates to the general election regardless of party.1

2

History and evolution

The primary system emerged in the late 19th century as a reform against party bosses who controlled nominations at conventions. Wisconsin enacted the first statewide direct primary law in 1903, following a model championed by Governor Robert M. La Follette. By the 1920s, most states had adopted primaries for state and local offices, but presidential primaries remained advisory until the 1960s. The 1968 Democratic National Convention, marked by protests over the Vietnam War, prompted the McGovern-Fraser Commission, which mandated that delegates be chosen through transparent, participatory processes, leading to the modern binding presidential primaries.2

3

Lesser-known aspects

Beyond the familiar state-level primaries, several niche variations exist. Runoff primaries, used in the South, require a second election if no candidate exceeds 50% of the vote. Nonpartisan primaries are used for municipal and judicial offices, where candidates are not identified by party. The presidential caucus, still used in Iowa and a few other states, is a party-run meeting rather than a state-run election, and it has been criticized for low turnout and complexity. Additionally, the invisible primary refers to the pre-primary jockeying for endorsements and fundraising that often determines the eventual nominee before any votes are cast.3

4

Impact and controversies

Primaries have significant effects on political representation and party cohesion. They can produce candidates who appeal to the party's base rather than the general electorate, a phenomenon known as polarization by primary. Turnout in primaries is typically lower than in general elections, often skewing toward older, more ideological voters. Critics argue that closed primaries disenfranchise independent voters, while supporters contend they preserve party integrity. Reforms such as ranked-choice voting and jungle primaries have been proposed to increase participation and moderate outcomes, but their adoption remains uneven across states.

Glossary

Closed primary
A primary in which only registered party members may vote.
Open primary
A primary in which any registered voter may participate, regardless of party affiliation.
Top-two primary
A primary in which all candidates appear on one ballot and the top two vote-getters advance to the general election.
Caucus
A party-run meeting where participants discuss and vote on candidates, often used in presidential nomination contests.

Primary election rules are determined by state law and party rules, leading to significant variation across jurisdictions.