who is generally not allowed to vote in a closed primary
Voting rights in the United States The Court has overseen operation of political party primaries to ensure open voting. While states were permitted to require voters to register for a political party 30 days before an election, or to require them to vote in only one party primary, the state could not prevent a voter from voting in a party primary if the voter has voted in another party's primary in the last 23 months.[10] The Court also ruled that a state may not mandate a "closed primary" system and bar independents from voting in a party's primary against the wishes of the party. (Tashijan v. Republican Party of Connecticut 479 U.S. 208 (1986))[63]