I came to the conclusion long ago that McCain, with the urging of Charlie Black, made the cynical decision to bring Sarah Palin on the ticket, not to win but to allow him to disengage from the campaign and revert back to his "bipartisan" back stabbing slithering. He knew he was going to lose to Obama and his staff knew. Palin became his convenient lightening rod to draw negativity away from him and allow a graceful exit back to the Senate chambers- which he essentially did when he suspended his campaign to push Bush's government bailout monstrosity.
Palin became his political piñata for the left and the GOP to beat on in effect, and his own staff willingly participated at taking their turn at bat on her.