¿Y si Santorum gana en Iowa?

Nate Silver:

First, Mr. Santorum does not just have momentum, but he has it at the right time — at a point in the campaign where conservative voters may be behaving tactically as they try to determine which candidates from among Mr. Santorum, Mrs. Bachmann, Mr. Gingrich and Rick Perry are most viable. Mrs. Bachmann in particular appears to be vulnerable because of a combination of soft polling and the defection of her Iowa campaign co-chairman, Kent Sorsenson. If Mr. Santorum were to pick up half of Mrs. Bachmann’s previous support, he would essentially be in an three-way tie for first place with Representative Ron Paul and Mitt Romney.

Second, Mr. Santorum is consistently showing good favorability numbers in polling of the state, and he also is frequently mentioned as voters’ second choice when pollsters ask about this. Second-choice preferences are not as important in the Republican caucuses because Republicans do not have a viability threshold in the Iowa caucuses, as Democrats do. Nevertheless, this increases Mr. Santorum’s potential to perform better than projected, particularly in light of potential tactical behavior on the part of voters.

Third, Mr. Santorum, who has strong support from evangelical voters, is the type of candidate who has traditionally overachieved his polls on caucus night.

Fourth, Mr. Santorum by all accounts has a strong infrastructure in Iowa. He therefore could have a strong turnout with plenty of volunteers who will vouch for his campaign on caucus night.

Our model currently gives Mr. Santorum a 7 percent chance of winning the caucuses, while the betting market Intrade gives him a 9 percent chance. I suspect that both estimates are too low.

But suppose that Mr. Santorum wins Iowa. What happens to his campaign then?

It might be instructive to compare Mr. Santorum’s position to that of another social conservative, Mike Huckabee. Mr. Huckabee was in a much stronger position outside of Iowa than Mr. Santorum is right now, polling at about 17 percent in national surveys at this point four years ago. Mr. Santorum, by contrast, is at only 4 percent support nationally in the latest Gallup poll. That Mr. Huckabee was not able to capitalize on his Iowa victory, despite seemingly being in a more advantageous position to do so, is one reason to be skeptical of whether Mr. Santorum would be able to, either.

With that said, there are two factors that Mr. Santorum has going for him that Mr. Huckabee did not. First, whereas Mr. Huckabee’s win had been expected in Iowa for some weeks in advance of the caucuses, Mr. Santorum’s would be a come-from-behind victory, something which has historically been associated with a larger post-Iowa bounce. Second, Mr. Santorum could potentially benefit from consolidation in the field if other conservative candidates like Mrs. Bachmann and Mr. Perry were to drop out of the race after a poor finish in Iowa.

Thus, it is a possibility that the Republican nomination could boil down to a two-way race between Mr. Santorum and Mitt Romney. Perhaps Mr. Paul would also be a factor in such a race.