What Happened to Palin?
Palin has morphed in a Bush-like character in this respect - she inspires great devotion among the GOP base, but turns off Dems and many independents.
She is officially the least popular of the four (Obama, McCain, Palin, and Biden) - see graph for details of net favorable/unfavorable ratings.
A lot can happen before November 4th and the debates will have a huge impact, but right now, it appears Palin was a bad bet.
Picking Palin was like drinking a can of Red Bull. For short time, you're moving along like the energizer bunny, but later, you're back where you started, but with an uncomfortable taste in your mouth.
This was by no means Palin's fault - the McCain campaign tried to fit a square peg into a round hole. By choosing the package her as an anti-earmark reformer, they ran straight into the weed whacker of reality. In this case, reality is accusations of misuse of her office in the service of some cronyism and to carry out some family grudges as well as a well documented thirst for earmarks.
Had they packaged her differently, she might not be seeing her unfavorable rating creep closer and closer to her favorable ratings (if Troopergate gets any worse, we may very well see this campaign end with Palin suffering from net unfavorables in a majority of national polls).