Party Primary

A party primary is a candidate-selection contest held within a political party to choose its nominee for a public office. Unlike a general election, the electorate is restricted to the party's affiliates or, in some systems, a wider pool defined by law or party rule. Primaries shift nominating power away from party leadership and toward voters or dues-paying members, a reform pushed in the United States during the Progressive Era in the early 20th century and later expanded after the 1968 Democratic National Convention through the McGovern–Fraser Commission reforms.

Primaries vary by access rules:

• Closed primary – only voters pre-registered with the party may vote (e.g., New York, Florida).
• Open primary – any registered voter may choose which party's ballot to take on election day.
• Semi-closed / semi-open – independents may participate but voters registered with another party may not.
• Blanket or "jungle" primary – all candidates from all parties appear on one ballot; the top finishers advance regardless of party (used in California since 2011 and Louisiana for state offices).

Primaries also differ by what is being awarded. U.S. presidential primaries allocate delegates to a national nominating convention, sometimes proportionally and sometimes winner-take-all. Congressional, state, and local primaries typically award the nomination directly to the plurality or majority winner, with some states (e.g., Georgia) requiring a runoff if no candidate clears 50%.

Outside the United States, internal candidate selection more often takes the form of party-member ballots or congresses rather than state-administered primaries. Argentina's PASO system (Primarias, Abiertas, Simultáneas y Obligatorias), introduced in 2009, is one of the few national, legally mandated open primary systems. France's Socialist Party held open presidential primaries in 2011 and 2017, and the UK's Conservative and Labour parties select leaders through member ballots rather than state-run primaries.

Primaries are studied for their effects on candidate ideology, turnout, and the relative power of party elites versus activists.