A Republican source close to her political team told CNN's John King that it was a "calculation" she made that "it was time to move on." The governor's "book deal and other issues" were "causing a lot of friction" in her home state, the source said, adding that he believes she is "mapping out a path to 2012."
To put it a different way: she wants to focus on making a lot of money instead of annoying things like governing. Then, she wants to run for President.
However, stepping down as Governor halfway through her first term won't give confidence to anyone who already had doubts that she could perform well as President. Maybe it is just because I am a gay Muslim Mexican socialist coastal terrorist secular liberal elitist who doesn't "get" middle America, but this seems like a terrible, terrible strategic move.
P.S.: Many commenters will inevitably say this is becuase of some sort of looming scandal. Maybe, but I am still going with Palin being a bit flaky and looking to cash in.