It's not mandatory, as many people register Independent and have no difficulty voting. The only restriction is in the preliminary elections to pick candidates (called Primaries) as these are functions of parties and can be (rightfully?) closed to non-party members.
This is quite similar to Canada, in that the party members pick candidates and vote for the leader. However, once the slate is tabled for each riding, it's purely a case of confirming you're registered on the list in the riding.
Not American so I'm curious: couldn't anyone just register as one party and vote in the primaries but then vote the other party at the actual election?
Yes, you can also register with a party and vote in the other party's primary if it's an open primary state. However, you are usually barred from voting twice in a primary, which means you need high confidence in the outcome of your preferred party's candidate to do this. Otherwise, you're throwing away your vote on that party's pick.
EDIT: I had to double check this before commenting, but in some states you don't even register with a party as far as the state is concerned (Georgia, for example, it's been 12 years and I'd forgotten). Though they still have the party primaries.
Comments
It's not mandatory, as many people register Independent and have no difficulty voting. The only restriction is in the preliminary elections to pick candidates (called Primaries) as these are functions of parties and can be (rightfully?) closed to non-party members.
This is quite similar to Canada, in that the party members pick candidates and vote for the leader. However, once the slate is tabled for each riding, it's purely a case of confirming you're registered on the list in the riding.
Not American so I'm curious: couldn't anyone just register as one party and vote in the primaries but then vote the other party at the actual election?
Yes, you can also register with a party and vote in the other party's primary if it's an open primary state. However, you are usually barred from voting twice in a primary, which means you need high confidence in the outcome of your preferred party's candidate to do this. Otherwise, you're throwing away your vote on that party's pick.
EDIT: I had to double check this before commenting, but in some states you don't even register with a party as far as the state is concerned (Georgia, for example, it's been 12 years and I'd forgotten). Though they still have the party primaries.