And I ask what might seem to be a stupid question because there are plenty of reasons that a voter could give to a pollster to justify voting for or against either candidate without having to admit to some bias or prejudice. For example...
...you could just say you're for McCain because of his experience and he's a war hero or that you're against Obama because of his inexperience and short time on the public stage. What would be the justification of telling a pollster that you were voting for someone that you were not? Why would large numbers feel the need to pretend that they were voting for either candidate?
And, besides, do pollsters even ask voters why they support one candidate over the other? If the only question is who will you vote for or who did you vote for, why lie?