There's very good odds that Newt Gingrich will be the Republican nominee. [View all]
Frankly, it's been obvious to me for a long time that Romney wasn't as "inevitable" as people imagined he was. Yes, the Republicans typically just nominate "then next guy in line." However, that was before "the next guy in line" was a Mormon and a flip-flopper. That 22% of people in the US who say that they would never vote for a Mormon? It's probably triple that in the Republican primary electorate. Romney can only win to the extent that the "not Romney" vote in the Republican base remains divided, so that he can "win" with 25-30% of the vote. It's not nearly divided enough for him anymore.
Meanwhile, I have no real expectation of either a brokered convention or a "dark horse" candidate getting nominated from the floor. The prospect of going to the beginning of September without a candidate would be disastrous for the Republicans; only slightly less so than pulling a bait and switch and attempting to push the party base into supporting a candidate who they had no choice in and was pushed on them by fiat. Look already how they're reacting to Romney, who's the choice of the party insiders, then multiply that by a hundred. You'd have open revolt, and if the candidate were deemed "insufficiently conservative" you'd probably see a very significant third party defection.
I think that Newt Gingrich is, right now, the odds-on favorite to be the Republican nominee for President.