A vote isn't a bet. You don't win a special prize if you happen to pick the winner. Voting for someone just because that candidate is more likely to win is just an appeal to popular opinion. If you vote for a candidate just because a lot of other people are voting for that candidate, then why bother voting in the first place?
Speaking of bets, 64.7% of people on Intrade betting on the election are for Obama, and 35.2% for Romney.