With Jon Huntsman's exit from the Republican primary race there are five main candidates left, and Mitt Romney holds a commanding lead among them with a 89.1 percent chance of gaining the Republican nomination, according to prediction market data. Ron Paul follows him at 4.1 percent, Newt Gingrich at 2.5 percent, and Rick Santorum at 1.2 percent. Since the dust settled in New Hampshire, Romney has slowly drifted upwards in his likelihood of winning the Republican nomination as it becomes more likely there would be no coalescing around a single challenger in South Carolina.
Sources: Betfair and Intrade
Huntsman's exit had little impact on the expected outcome of race, as there was little expectation that he would ultimately prevail after his third place finish in New Hampshire. Yet, it may have had a short term impact, making it just a little easier for Romney to become the presumptive nominee after South Carolina by leaving Romney as the lone moderate in the race compared to the others.
As you follow the lead up to the South Carolina votes, remember that Gingrich and Santorum are extremely likely to combine for more votes in South Carolina than Romney. Yet, neither of them has been able to gain the upper hand as the conservative choice. Gingrich has been polling slightly higher, according the aggregated trends of Real Clear Politics. Yet, Santorum recently received a near-consensus endorsement from evangelical leaders. As David Pennock pointed out, that may have been the best outcome Romney could have hoped for, as it may have hopelessly divided the conservatives ahead of the South Carolina primary. Perry is likely to be a distant fifth in South Carolina, as he is not deemed competitive anymore.
Ron Paul is now the most likely Republican alternative to Mitt Romney; he is also currently in second place with votes and delegates having finished third in Iowa and second in New Hampshire. He is the only other candidate with ballot access in every primary, and he has massive funding and organizational support. He has vowed to fight to the end of the Republican primary season, as he has done in the past.
Yet, he is more likely to mount a third party campaign, about a 20 percent chance, or fight to affect the Republican platform, than he is to win the nomination. His libertarian views are simply too at odds with the mainstream conservative Republicans. Just not so far off that he couldn't make life difficult, or at least interesting, for Romney down the road.
David Rothschild is an economist at Yahoo! Research. He has a Ph.D. in applied economics from the Wharton School of Business at the University of Pennsylvania. His dissertation is in creating aggregated forecasts from individual-level information. Follow him on Twitter @DavMicRot and email him at firstname.lastname@example.org.