Which primary allows any voter to participate regardless of party affiliation?

An open primary is a primary election in which any registered voter can participate regardless of their political party affiliation. This means that voters are not required to be registered members of a particular party to cast their ballots in that party's primary election. This system encourages greater participation and allows independents or members of other parties to engage in the choice of candidates for a specific party, which can lead to a more inclusive electoral process.

In contrast, closed primaries restrict participation to only those voters who are registered with a specific political party, thus limiting the decision-making to party members. Run-off primaries occur when no candidate receives the required majority in the first primary, necessitating a second election, usually between the top candidates. A caucus is a different type of electoral event, where party members gather to discuss and select delegates rather than using a conventional voting process. These distinctions highlight why an open primary is characterized by broad voter participation.