Sarah is un-electable. She may have had a chance if she had stayed as governor to finish her term out, which she was elected to do and had an obligation to her constituents to complete.
There is no way, in my opinion, an adversary could not use that against her to destroy any sense of obligation or willingness to complete a tough position to the end.
Face it, when a better, more profitable, and easier opportunity came along, she bailed.