We've always maintained that Republicans simply won't buy into Mitt Romney. While the news media has jumped on the "Mitt Romney has overwhelming momentum and will be the nominee" bandwagon, we continue to maintain that the Republican nominee will be decided by what "anti-Romney" candidate the Republican party coalesces around.
While there has been a lot of attention paid to Romney's gains in Iowa, Mitt Romney and Newt Gingrich are only about two points apart today in the only poll that counts - Gallup (Gingrich has 24%; Romney has 26%). This is actually +1 for Gingrich. Gingrich still dominates in South Carolina and Florida - and consequently most of the Southern states. Since the creation of the South Carolina primary, a Republican candidate has not been able to become the nominee without it -- a sure sign that conservatives of the Southern and Midwestern variety are the true swing votes in the Republican Party.
We will also have to pay very close attention to the performance of Ron Paul and Rick Santorum. If Ron Paul wins, there will be a lot of speculation about his performance in later primaries. It will also make Mitt Romney look bad because his campaign has significantly raised expectations about his performance. But if Rick Santorum gets first, second, or third, his campaign will get a boost in momentum because expectations for him have been so low. Because the really conservative wing of the party is looking for a candidate, this could either split the conservative vote among the non-Romney candidates or unify the anti-Romney vote around Santorum, ending the campaigns of Gingrich, Bachmann, and Perry.
And finally, if Mitt Romney does win in Iowa, momentum will simply follow the pattern it always has -- the moment Mitt Romney gets more scrutiny, the more determined his opposition becomes to unite around one of his opponents.