Do not think, when you vote, that you are just voting for yourself. For every person on the edge, there are 1000 other voters who will vote the same way you do. So if you stay home, thinking that your vote won't count, you are behaving exactly the same as 1000 other voters who will vote as you do. If, however, you hold you nose and vote for the only practical alternative to an unacceptable option, then there will be 1000 people joining you in your vote.
Why do polls matter? Because polls influence the weak willed to vote or not vote as they see the wind blowing. Why is the mainstream media so insistent on repeating that McCain is behind in the polls? Because in this case, saying makes it so. It is the Big Lie. The only countermeasure against the Big Lie is the Little Truth. You must vote. For each of you who votes, you will be joined by 1000 non-Objectivist voters. This is not science. It is democracy. Democracy is an exercise in applied practical social-metaphysics. The winning vote is yours. What are you going to do with it?