Primary election at which voters are free to choose which party they wish to select the candidate for. Subject to manipulation, as supporters of one party can attempt to obtain the nomination of the weakest candidate of an opposing party by voting in their opponents' primary.
A type of direct primary open to voters regardless of their party affiliation. Voters need not publicly declare their party affiliation but must vote for candidates of only one party. The opposite is a closed primary, in which only registered members of a party may vote.