Strongest- Pawlenty. Governed a Democratic-leaning state for two terms.
Weakest- Huckabee. Crazy, governed a state most people view negatively. Also, scary to the non-base.
In between:
Romney- Would be strongest, but people are bigots and may vote against him solely because he is a Mormon.
Palin- Like Huckabee, but with a little more stupid and a little less crazy. She only gets the edge because Alaska's image is a little better than Arkansas'. Also, she may not even run, and if she does, she'll mostly be doing it for the book deal.
Johnson- Nonfactor, since he's like Paul with even less name recognition.
Newt- Smartest of the bunch, but also thoroughly unlikeable.
Thune- From small state, so not well known. However, he did beat Tom Daschle. While this won't help him at all in the general, this possibly could give him a chance in the primaries.
Why is that people keep on forgeting that he came out of baisicly nowhere and won as a republican the gubernatorial race in a state 2-1 democratic, the proceedid to win re-election.