Palin only does that because she owes her recognition to Mc Cain, and she knows it. She doesn’t agree with a lot of Mc Cain, but she knows she’d still be the little known governor of Alaska if it weren’t for him. I’m sure she has stressed over it.
As the political climate is very favourable to Republicans, this is a historic opportunity to dump McCain and get a conservative republican in his place.
McCain knows this and hence he is using every dirty trick in the book etc, Sarah has made the wrong choice here by backing McCain in this primary.