There are a lot of stupid things that people do, but the most enraging thing is voting wrong. There are seemingly endless justification for voting wrong, but the worst is voting for the person that you think will win. Why would someone vote for someone that was going to win? Your vote means nothing if it doesn't change the effect of the election. It's not like you get a prize if you pick 'the right guy' or something.
Some will point out that your chance of effecting the election is zero, regardless of whom you vote for. That's true.