Uh, how many terms had she served when she was picked for VP?
Now tell me why you think that the most popular governor in the United States was not a shoo in for reelection in your scenario, the fact is that she would have been unbeatable for reelection, as it is she still was unbeatable when she actually did leave after the 2008 election and all the constant national effort to weaken her in her office.
"The fact of the matter is that she wouldn't be where she is today without the star-making cachet of having been chosen as McCain's VP. Without that, she'd be a one-term governor of Alaska"