I'm a registered Democrat in Massachusetts, a state with semi-open primaries such that registered voters can only vote in their party's primary, but unaffiliated voters can vote in any primary. I'm not happy with the Democratic Party this election season and want to send a message in the form of having as little to do with them as possible, but I still want to be able to vote in future Democratic primaries. Is there any reason why I shouldn't change my registration to unaffiliated?
People register with political parties because of that party matches their own internal identity, not (usually) because of strategic or rational reasons.
Political scientists differentiate between two different, but important ideas:
- Party membership is what party a person formally belongs to.
- Party identification is what party a person identifies with.
Party identification is psychological. It has to do with accumulation of a person's experiences and thoughts over a lifetime.
Why does party identification matter? Because most people register for the party the identify with, even if they never vote. It isn't the strategic value of being able to vote in a closed primary that drives membership, but a perceived intrinsic link with what that party stands for.
The seminial work on American voting, The American Voter has an excellent section covering party Id and membership. If you'd like to really delve into the subject, that is a great place to start.