As far as Governors go (best presidential rehearsal) Governor Palin seemed to be the best in the land, I live under failed Governor Arnold Schwarzenegger, I know about Governor Mitt Romney being a failed Governor, no one that I know stood out more than Palin as Governor, if you can think of one or two that did, then name five more.
The most important thing in a President is to represent America in a way that actually represents the United States of America, Kennedy, Johnson, Nixon, Ford, Carter, H. W. Bush, Clinton, I lived under them all and I would prefer Palin over any of them. Gore, Dukakis, Mondale, Kerry, McGovern etc., same thing.
She may be better than the 2 you mention, but there are Jindhal, Mitch Daniels, Haley Barbour, and few others like Bill Owens and Jeb Bush who have been and are good as well. Also, I hope and expect the new Gov of Virginia McDonnell to also be a solid “A” level Governor. There are some that are almost-as-good: Pawlenty a B+, but still good. Huntsmann of Utah also good and v sharp, but a bit on the squish/corporate side (aka another Romney-type in multiple ways).
Of these, I think several are no-go for 2012, but Palin, Jindhal, Daniels and Pawlenty are possible contenders.
“I lived under them all and I would prefer Palin over any of them.”
Well, I prefer a bubble bath to getting splinters under my fingernails too (the only decent ones in that list were Ford and GHWBush, egads, what a sad record).