A sitting Governor, not an already ran, not someone who quite (for whatever allowed for reasons) once their job got to hard for them (be that professionally or personally...hell running for POTUS will only be harder/worse). There are several "R" Governors that will be in strong positions come 2012.
Read Rendesvous with Destiny. The consensus in 1978-80 was that Reagan would lose...overwhelmingly. All the polls said so. And Jimmy Carter couldn’t wait to run against him.
Was Reagan a sitting Governor when he ran against Carter? No, but he was a former Governor - just like Sarah Palin.
Had Reagan run for the presidency prior to 1980 when he ran against Carter? Why, yes he had. Just like Sarah Palin.
And you may as well drop the "quitter" meme. Only you, the Romneybots, and the Obots are still drinking that debunked swill.
Outside of politics ?
Sarah Palin is dominating politics. Sarah Palin is probably the reason Nikki Haley is going to be the next governor of South Carolina.
You want her to leave politics ?