I know it's a lot of work for you guys to manage this thing so I totally get if this isn't doable but how about removing the member names from the entries in the voting thread, disabling comments in that thread, and hiding the submission thread once the vote goes up? This would remove most of the bias in the voting (people could still see which is theirs and beg others to vote for them but that is explicitly stated to be against the rules).
I still think the best way is to have the contest sponsor pick the winners but if you leave it at voting I think the finalists need to be as anonymous as possible.
I still think the best way is to have the contest sponsor pick the winners but if you leave it at voting I think the finalists need to be as anonymous as possible.