Jonathan Martin has the story here. For semi-professional Palin watchers like myself, this doesn't come as much of a surprise. On a recent trip to Alaska for my forthcoming book on the governor, I picked up a lot of chatter to the effect that Palin wouldn't run for a second term.

Palin's term ends in December 2010 -- right around the time when the next presidential cycle begins. She'll have plenty of time to spend in the Lower 48, in Iowa, New Hampshire, and South Carolina in particular.

UPDATE: Time's Mark Helprin reports that Palin will be stepping down in a few weeks. More is sure to come.