Palin would be an unmitigated disaster. I don't understand why some on the right think she is a viable candidate. I'm even more perplexed by the notion that liberals fear her. Ask Democrats who they want to run against in 2012, it's her. People like Olbermann don't rip on her because they fear her, they rip on her because of the stupid shit that comes out of her mouth. That goes for Michelle Bachman as well.
I don't see Pawlenty or Gingrich being viable either, they're both too far right to capture enough independents. I know this board is full of partisans (from both sides) but the bottom line is that this country is 30/30/40 conservative/liberal/independent (some of whom lean left or right but will vote for either party depending on the candidate) People like Palin or Gingrich could never win a general election for the same reasons someone like Dennis Kucinich never could. They're just too far out there for the mainstream. The Republicans would do themselves a major disservice by turning the primaries in to a conservative circle jerk.