- Democratic congressional and state primaries: mixed
- Republican congressional and state primaries: closed
- Democratic Presidential primary: mixed
- Republican Presidential primary: closed
- Voters may or may not choose to affiliate with a political party, however, affiliation with a party is required to vote in Republican primary elections. Independent voters may vote in the Democratic primaries.
- 16% of Oklahoma voters are registered as independent.
Details of voting in congressional and state primary elections:
- Independent voters may vote in the Democratic Party primaries but voters must affiliate with the Republican party to vote in the Republican Party's primary.
- Voters cannot change party affiliation between April 1 and August 31 in even-numbered years.