Palin is nobody. She’s a small-town mayor who managed to get into the Alaskan Governor’s Mansion in 2006 for being less somewhat less corrupt than Alaskan Republicans. That’s it. People were ticked off at Republican corruption, she positioned herself as a non-corrupt Republican, and got voted in in a traditionally Republican state. I could see her becoming a good Governor in time, better than most Republicans at any rate, but this is not that time.
And she could have her finger on the button if anything happens to McCain. It would be like that one Heinlein story in Expanded Universe, except somehow LESS plausible.
In the story refered to, it was a Black woman who got to be the token vice-president and then the real president got assasinated and the real powers in the party expect her to give up her job because she obviously wasn’t expected to actually govern (which some commentators also expect of Palin if McCain kicks the bucket). In true Heinlein fashion she of course refuses, kicks out the corrupt elements and starts putting the country back on the right track, which IIRC meant getting back on the gold standard, putting the navy in charge of nuclear power because they had such a good track record with it and finally getting the colonalisation of space going properly. Somehow I doubt Palin would do as well.