After the election, I will poll Manifold users to ask how they voted (the same poll as used for this market). I will resolve PROB to the fraction who voted Republican vs. the fraction who voted Democrat. (Other parties and people who didn't vote are ignored.)

The poll will not be anonymous, and if I find out that anyone answered the poll differently from how they actually voted, I will consider that dishonorable. Realistically though, I have no way to enforce accurate voting.