Pawlenty has no distinguishing traits. He is like Romney without a record in a populous state, with no "businessman" credentials, without frontrunner status, without media backing, without millions of dollars to self fund with. Hell, Romney himself, for all his advantages, is at the top of his game right now. He has enough skeletons in his closet to fill a graveyard, and the instant his opponents start going after him his "frontrunner" status is going down the toilet (along with most of his other advantages, like being considered "serious" by the media).
Oh, and if Palin and Huckabee don't run, their support mostly goes straight to Gingrich, Romney, and Paul (in that order), them being the "serious candidates" (Paul less so, but he is certainly more front runnerish than the second tier clowns like Pawlenty posturing and posing as utterly indistinguishable tea party clones with no strong sets of allies). And Romney is almost certainly going to see his support from Palin and Huckabee disappear once his opponents (in this case, Gingrich and Paul) begin attacking him (especially when they focus on his flip flopping on abortion, a huge issue among Huckster supporters). Gingrich would get support from rank and file Republicans and would probably be the default mainstream candidate if Romney fell apart. Romney is currently doing well with moderate Republicans and conservatives who don't know better. Paul is getting the usual dedicated Libertarian and extremely Conservative supporters (think Birchers) in addition to anti-war Republicans (a growing force). He will probably get plenty of support from Huckster supporters who don't go for Gingrich (Huckabee and Paul have a bit of a strange relationship: they made deals in some of the primaries earlier, Huckabee stole a bunch of Paul's talking points a while back, Huck doesn't mock Ron like, say, Romney does, and going by online Huckabee supporter forums, most of his supporters are also quite fine with Ron Paul too, so Huckabee not running would be great for Paul). Palin's supporters are a complete wildcard, since I dunno what they think she stands for, but I don't see her backing the "establishment" so she would either back Paul (a huge bonus for him) or she wouldn't back anyone.
Anyway, unless one of the second or third tier candidates actually distinguishes themselves (as Paul did in 2008 with his unusual views gaining him fame/popularity and Kucinich partially managed for the same reasons), it looks like a race without Huck and Palin would be a reasonably tight race between Romney, Gingrich and Paul.
Not sure why you think Gingrich is better at campaigning than Barbour. Newt's been out of the game a long time and I don't think many people like him, even in the GOP.
