who is allowed to vote in an open primary
Open primaries in the United States The open primary could be seen as good for voter participation. First, the open primary allows nonpartisan or independent voters to participate in the nominating process.[3] If these voters are allowed to help select the nominees then they may be more likely to vote in the general election, since one of the candidates could be someone the non-partisan voter voted for. Also, a moderate member of one party may agree more with a candidate for the nomination of another party. This voter will have more of an incentive to participate in the general election if there is a nominee whom he or she agrees with.[3]
Primary election Candidates for U.S. President who seek their party's nomination participate in primary elections run by state governments, or caucuses run by the political parties. Unlike an election where the only participation is casting a ballot, a caucus is a gathering or "meeting of party members designed to select candidates and propose policies."[21] Both primaries and caucuses are used in the Presidential nomination process, beginning in January or February and culminating in the late-summer political party conventions. Candidates may earn convention delegates from each state primary or caucus. Sitting presidents generally do not face serious competition from their party.