I have seen several commentaries recently on how best to reform Maine’s primary election system. At present, voters may vote in a primary only if they are enrolled in a political party; a voter may only vote in the primary of the party in which he or she is enrolled.
If a voter is not enrolled in a political party, then he or she may do so on Election Day, and then unenroll many days later. This is not fair to unenrolled voters since many of them do not want to associate with a political party.
The League of Women Voters of Maine, after studying ways to improve this system, decided to support semi-open primaries. In a semi-open primary, an unenrolled voter may vote in a political party of their choice without the need to enroll in that party.
Party members may only vote for their party candidates. This seems the best alternative to me, because it does not allow voters enrolled in one party to vote in the primary of another party for strategic reasons, for example to help elect the worst candidate for that party.