It occurred to me halfway through the first presidential debate that I did not care about the debate. Not one bit. Why should I? I know that regardless of what The Other Guy said, I would still vote for My Guy. The Other Guy could literally hand out puppies and promise "free foot rubs for all Americans," and it wouldn't matter.
There was nothing The Other Guy could say that would change my mind. And I assume the same was true for those who intended to vote for The Other Guy. Can you see a Romney supporter deciding to vote for Obama? Or an Obama supporter deciding to vote for Romney instead? No. That's just not how the world works.