- Democratic congressional and state primaries: mixed
- Republican congressional and state primaries: mixed
- Democratic Presidential primary: open
- Republican Presidential primary: open
- Indiana has nonpartisan registration. There is no option to affiliate with a political party on the voter registration form.
Details of voting in congressional and state primary elections:
- Affiliation with a party is not required to vote in primaries. However, voters can only choose the primary ballot of the party who recieved a majority of their votes in the previous general election, and voter records are kept as public information.
- If a voter did not vote in the last general election, they must "intend to vote for the majority of the nominees on their desired party's ballot."
- Voters can be challenged by another eligible voter on suspicion of perjury.
- This system is an attempt to get voters to vote along party lines, but is not easily enforceable.