How Missouri's Primary Election Works

Missouri uses an open primary election system. Registered voters do not declare a party affiliation when registering to vote. On primary election day, voters may choose either the Democratic or Republican primary ballot, but they may only vote in one party's primary.

Missouri does not hold primary runoff elections. Candidates only need to receive a plurality of the vote to win their party's nomination, meaning the candidate with the most votes advances to the November general election even if they do not receive an outright majority.