Poll - Canceling members' votes

I would like a way for me, as an admin, to be able to see how other members voted in a poll, and have a way to cancel out their vote. My site is based a lot on rating photos in a challenge every week. I was doing it through the gallery, but the gallery just doesn't do what I need it to do. So I have changed it so the voting happens through the message boards. So each picture has a poll so members can vote on a 1-10 scale. I can't stop them from voting on their own picture right now, but I don't want them to be able to. This is one of the suggestions I offered for the gallery, but it hasn't happened yet. So if I could see who has voted, I don't really care if I can see what their vote was or not, and had a way to cancel their vote, that would be nice.