I think the Maine'ahs have the solution. It would require registration by party, though.
Me: Question about absentee caucusing from Washington State.
We allow people to send in a form only if they are disabled, in the military or can't go for religious reasons. I've just seen other posts on GD:primaries implying that Maine lets anybody who wants to do an absentee caucus. What are the criteria? Is there registration by party in Maine? There isn't in Washington.
Maine'ah #1: Yes, registration by party.
And you can get an absentee ballot for any reason. The only drawback for the voter is that, if they vote absentee, they can't take a second choice if their candidate comes up short in the first go-round.
Me: So, in order to get an absentee choice you must register as a Dem?
Maine'ah #1: Yes.
In order to vote in the caucus at all, you have to be a registered Dem. But, you can register the same day. You can't however, change your party enrollment the same day.
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=156x5782