I can't know for sure without getting into John McCain's mind. I'm not going to do that, it's a dark and frightening place. But, my gut is telling me that his veep pick was not a well thought out decision. Apparently McCain, only now, is getting around to vetting Sarah Palin.
McCain's first act as president, the selection of his running mate, was impulsive. He acted without thinking, without considering all of the ramifications. Impetuousness is just the personality trait you want in a man who wants war with Russia and has his finger on the nuclear button.