"For me, Palin's problem as a candidate for national office in 2008 was that she had not been sufficiently tested. Her problem as a candidate for national office in 2012 is that she has been tested and failed. She failed, that is, to complete her one term as governor of Alaska. It's not clear why, but the failure seems to have been due to some combination of insufficient commitment to the job she had sought and inability to deal with attacks that likely pale in comparison to those she would face as president."
Not a shocking notion, but the author may surprise you.