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.
He rode a wave in 1994 and gubernatorial elections generally aren't as ideological as, say, senatorial elections. It's not uncommon for a Republican to get elected in a predominately Democratic state, and vice versa. One Republican or another, for example, has been governor of Massachsetts for 17 of the last 30 years. Look at Weld's reelection percentage. Do you think that he would win the Republican nomination?
Winning the presidency - hell, even the nomination - is an entirely different animal. Once his views on things like the legalization of marijuana becomes fodder - and you better believe that Romney, Pawlenty, and the like will carpet-bomb early states during the primary - what little support will have amongst the elderly who constitute the lion's share of your party's primary voters will drop like a stone.
We don't say Johnson's a non-factor to annoy you or because we're forgetful; we do so because he's a non-factor.