- Democratic congressional and state primaries: mixed
- Republican congressional and state primaries: mixed
- Democratic Presidential primary: closed
- 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 primary elections.
- 37% of Maine voters are not enrolled in a political party.
Details of voting in congressional and state primary elections:
- Voters must affiliate with a party in order to vote in that party's primary.
- "Unenrolled" voters may register with a party on primary day to vote in that party's primary.
- Any affiliated voter who wishes to change party enrollment must do so at least 15 days before the primary election.
- A voter may change party enrollment again after 3 months from the date on which the voter last changed parties.