While Bachmann, Santorum and Cain (and Palin if she gets in the race) are pretty close to being pure conservatives, can they appeal to enough independent and/or moderate voters... enough of them to win the election?
No matter how anyone feels about any of the 7 candidates who debated last night, any one of them would be far better than Obama, and we all know that if Obama wins re-election, this country is screwed.
Palin has a proven record of appealing to a broad politial spectrum and concensus-building with high job performance approval ratings.