What if the ticket is McCain/Romney?
If I lived in an important state like Florida, I'd hold my nose and vote for him.
But since I live in Massachusetts, which will go Democrat anyway, it really doesn't matter who I vote for, or even whether I vote at all, in the presidential race.
So I while I will definitely vote for whoever ends up running against John Kerry in the Senate race, I won't be voting for McCain no matter who he runs with.
And by the way, he won't be running with Romney, bet on that.