From a change-of-heart column by Richard Cohen that you should read:
McCain has turned ugly. His dishonesty would be unacceptable in any politician, but McCain has always set his own bar higher than most. He has contempt for most of his colleagues for that very reason: They lie. He tells the truth. He internalizes the code of the McCains — his grandfather, his father: both admirals of the shining sea. He serves his country differently, that’s all — but just as honorably. No more, though.
. . .
Palin, no matter what her other attributes, is shockingly unprepared to become president. McCain knows that. He means to win, which is all right; he means to win at all costs, which is not.