Newt Gingrich is again the favorite to win the South Carolina Republican primary

David Pennock
Computer Scientist
The Signal

Two days ago, Mitt Romney was looking at a clean sweep of the first three contests of the 2012 primary. With polls opening at 7 a.m. EST tomorrow, he's now looking at going one-for-three. First, he lost his technical 8-vote victory in Iowa to Rick Santorum (though let's face it: It was a tie.) Now, his once dominate odds of winning South Carolina have dwindled to 35 percent as of this writing, 30 points behind rival Newt Gingrich.

Newt Gingrich is two-for-two in standing ovations in the last two Republican presidential debates. After his well-received performance on Monday in Myrtle Beach, Gingrich earned a modest 3 percent boost in our prediction model, computed as the average of political stock markets Intrade and Betfair. But after Thursday night's debate in North Charleston, featuring a thrashing of CNN moderator John King over a question about his ex-wife's allegations that he asked for an "open marriage," a flurry of trading gave Gingrich a massive 20 percentage-point boost in the markets. In a matter of hours, Gingrich flipped entirely with Mitt Romney, going from a 40-60 underdog to become a 60-40 favorite in the markets.

Candidates' chances to win the South Carolina Republican primary, as of 1/20/2012
Candidates' chances to win the South Carolina Republican primary, as of 1/20/2012

Gingrich is doing exactly what Romney hoped he wouldn't or couldn't: consolidate social conservative voters in South Carolina, previously split between Gingrich and Rick Santorum. Romney has never polled above 50 percent in the state and, even at his highest likelihood to win, was expected to win by a plurality, not a majority. Now that Rick Perry is out and Santorum has flatlined, Gingrich has succeeded in cobbling together the anti-Romney forces, enough to possibly win outright.

Even if he does win in South Carolina, however, we currently rate Gingrich with only a 15 percent likelihood to win the GOP nomination overall to Romney's 79 percent.

Rick Santorum meanwhile fought desperately to "un-consolidate" the voters, arguing forcefully that he was the only candidate on stage with an unblemished conservative record on healthcare and abortion. He also warned the GOP electorate of the danger of nominating Gingrich, whom he said tends to speak glibly, consequences be damned. With Gingrich, there's always that "worrisome moment that something's going to pop. And we can't afford that in a nominee," Santorum said.

As usual, Ron Paul's passionate and committed support has held fairly steady in the markets. Not so for the other candidates, whose prospects have swung wildly throughout this primary season, often in reaction to debates--never more dramatically than last night.

David Pennock is a research scientist at Yahoo! Research. Follow him on twitter @pennockd.

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