Is she gearing up for a run at the 2012 Republican nomination? Could be, but quitting before finishing one term as governor doesn't seem to add any gravitas to her profile. I'm sure lots of advisors have been whispering in her ear that she's ready for the big show, but she isn't.
Perhaps she's tired of taking shots for herself and her slightly nutty family, which is understandable, but then the question becomes, "What's next?" Any public office will keep her in the spotlight and open her up to similar attacks. She's signed a book deal, so maybe she's going for the dollars here and will become a Newt Gingrich-like poser, lecturing about what the party needs to do while not actually getting dirty hands by, you know, doing it.
Upcoming scandal? Maybe - there are a lot of people leaking campaign stories in advance of an upcoming book on the subject, and there's a chance that someone found a spark of fire beneath the billowing clouds of rhetorical smoke.
I think it's a combination - she's going for the money while she can, like a true conservative, and testing the waters for a possible run for 2012. She's being closely watched in Alaska, and is subject to strict ethics rules. By becoming a private citizen for awhile, she has fewer restrictions on her earnings, her travel, and her message. It will probably end up being a disastrous combination, since she seems unable to grasp the concept of ethical behavior, and there will be a cottage industry springing up to track her every step.
More to come, I'm sure.
