COLUMBIA, S.C. - Capping off the wildest week yet of the race for the Republican presidential nomination, the country's first primary south of the Mason Dixon line takes place today in South Carolina, a state known for picking winners.

The victor of South Carolina's GOP presidential primary has gone on to win the nomination since the primary was established in 1980, making today's contest that much more significant.

The primary comes at an eventful time in the Republican race.

When the candidates left New Hampshire just last week, former Massachusetts governor Mitt Romney was flying high, fresh off a resounding win in the Granite State and believed to be a narrow 8-vote victor in Iowa's Jan. 3 caucuses.

Newt Gingrich, meanwhile, was struggling after two disappointing showings to kick off the primary. To make matters worse for the former House Speaker, Romney held a comfortable double-digit lead in polls out of South Carolina.

My how things have changed.

As voters head to the polls today, Gingrich, not Romney, is now the favorite in South Carolina. Two commanding performances by Gingrich in the past week's debates helped. So too may have the fact that he hails from neighboring Georgia. Not even his ex-wife's claims that he lacks the moral character to be president slowed him down.

After Gingrich's second wife Marianne told ABC News in an interview that Gingrich sought an "open marriage" agreement so he could have a mistress and an ex-wife, Gingrich delivered a resounding response to the charges when asked about them at Thursday's debate in Charleston.

"I think the destructive, vicious, negative nature of much of the news media makes it harder to govern this country, harder to attract decent people to run for public office, and I am appalled that you would begin a presidential debate on a topic like that," Gingrich replied.

"To take an ex-wife and make it [an issue] two days before the primary a significant question in a presidential campaign is as close to despicable as anything I can imagine," he said.

"The story," he emphasized, "is false."

Romney, for his part, hardly enjoyed a stellar week in the run-up to the primary. He caused a stir when he revealed that he paid a 15 percent tax rate and, when questioned about releasing his tax returns on Thursday, was even booed by the crowd. On top of all that, it turned out Rick Santorum had in fact defeated him in Iowa. Suddenly the air of inevitability around the former Massachusetts governor seemed to start dissolving.

Another boost for Gingrich - and blow to Romney - came when Texas Gov. Rick Perry dropped out of the race and endorsed Gingrich. Perry's departure could help consolidate the anti-Romney conservative vote around the former House Speaker.

A Ham House showdown was narrowly averted this morning when both candidates planned campaign stops at Tommy's Country Ham House, with Gingrich's staff claiming they set up the event first.

But Romney hit the ham house early Saturday morning and the candidates never crossed paths.

"Where is Mitt? I was hoping for a debate!" said Gingrich.

Read more about the ham house showdown.

On Friday night Romney held one of the liveliest rallies of his campaign in Greenville, with the crowd of about 300 going absolutely wild. At one point the crowd started cheering "We need Mitt, we need Mitt!" To which Romney responded frankly, and without missing a beat: "Do you know what? You're going to get me?"

"This is the best audience I've visited in a while," he said.

Romney rolls into the primary knowing that success here will virtually lock up the nomination for him. Another win in Florida's primary on Jan. 31 would be the nail in the coffin.

But the rapidly changing GOP race may now be heading in the direction of Romney's opponents, especially Gingrich. With Michele Bachmann, Jon Huntsman, and now Perry out of the race, Gingrich is now poised to make a strong bid to emerge as the alternative to Romney.

Its clear now the race will move in earnest beyond South Carolina since Romney verbally committed to take part in a debate Monday in Florida.

In the past week, there have been signs that Romney's lead in the Palmetto State is shrinking, if it hasn't evaporated altogether. According to a CNN/TIME/ORC poll released Thursday, Romney leads Gingrich 33 percent to 23 percent among registered Republicans likely to vote. But a handful of polls on Friday showed Gingrich had overtaken Romney altogether, taking a 6 point lead into today's primary.

Gingrich has gone as far as to acknowledge that a victory by Romney would virtually lock up the GOP primary for Romney, even while saying that he intends to move on to Florida come Sunday no matter what happens today.

Even with the suddenly close battle for South Carolina, the Romney camp will likely take heart in the latest poll results out of Florida. The CNN/TIME/ORC poll revealed the former Massachusetts governor with a commanding lead there, up 43 percent to 19 percent over Santorum, with Gingrich in third at 18 percent. The Florida primary is set for Jan. 31, but first things first - the battle for South Carolina is far from over.

Matthew Jaffe is covering the 2012 campaign for ABC News and Univision.