01/20/2012 10:38 EST | Updated 03/21/2012 05:12 EDT

Gingrich moving ahead of Romney as front-runner struggles with tax returns issue

CHARLESTON, S.C. - Newt Gingrich could be poised to deliver a stunning setback to Republican presidential front-runner Mitt Romney, surpassing him in a handful of polls with just one day until the high-stakes South Carolina primary.

After two solid debate performances from the thrice-married Gingrich in a state that's big on family values, the former speaker of the House of Representatives has been gaining ground on his rival even amid tawdry allegations from one of his ex-wives that he wanted an "open marriage."

South Carolina is considered a do-or-die primary for Republican presidential hopefuls. Since 1980, every candidate who wins the contest in the socially conservative state has gone on to win the party's nomination.

Romney had hoped to seal the deal on the nomination by winning South Carolina, but was stoic Friday while conceding he's now in a tight sprint to the finish line with Gingrich.

"Frankly, to be in a neck-and-neck race at this last moment is kind of exciting," Romney said as he campaigned in North Charleston.

Gingrich, meantime, made a campaign appearance in Walterboro, S.C., with family members by his side, including his 10-year-old grandson, one of his daughters and his brother — a clear attempt to show the state's voters that his family loves and supports him.

Earlier in the day, Romney's attack dogs were out in full force, trying to inflict some damage on the surging Gingrich.

Romney supporter John Sununu, the former governor of New Hampshire, portrayed Gingrich as an egomaniac with delusions of grandeur.

"You can't have somebody that's really as irrational and perceives himself as Winston Churchill or the equivalent of Margaret Thatcher or Charles de Gaulle," Sununu told CNN.

They also set up a morning conference call with three anti-Gingrich congressional lawmakers who assailed his past support of so-called earmarks, federal funds that pay for the pet projects of legislators in their home districts and help them get re-elected.

It's a term that's become a dirty word to Americans. And Gingrich was "really the granddaddy of earmarks," said Arizona congressman Jeff Flake.

Romney's campaign has also called upon Gingrich to release documents on the inquiry that saw him pay a $300,000 fine for violations of House of Representatives ethics rules.

But Romney, a multi-millionaire, has stumbled badly on questions about when he'll release his tax returns. The former Massachusetts governor was also the subject of allegations earlier this week that he's sheltered some of his millions in a Caribbean tax haven.

Romney held a commanding lead in most South Carolina polls just 10 days ago. But a new Clemson University poll of the state's primary voters has Gingrich at 32 per cent among, ahead of Romney at 26 per cent.

The latest Public Policy Polling survey, meantime, puts Gingrich at 34 per cent, with Romney at 28 per cent.

Other polls have suggested a similar upward trend for Gingrich, while the fortunes of Rick Santorum, a staunch social conservative, have fallen. He's now in fourth place in most polls behind libertarian Ron Paul.

Monday's Myrtle Beach debate marked the first time Romney has faced the tax-returns question in South Carolina, and though he said he'd probably release them soon, he appeared rattled by the query.

Some have suggested he's nervous about releasing them in South Carolina because they will reveal he's donated a significant amount of money to the Church of Jesus Christ of Latter-day Saints. Sixty per cent of South Carolina's Republican primary voters are evangelicals with a distrust of Mormonism.

During Thursday night's debate in Charleston, Romney was roundly booed for replying "maybe" when asked if he'd release several years of tax returns.

Gingrich pounced.

"If there's anything in there that's going to help us lose the election, then we should know it before the nomination," he said to cheers.

Gingrich, in fact, got several standing ovations for some of his remarks, just as he did three nights earlier when he snidely disputed a suggestion that his recent comments about black people and food stamps were racist.

The one-time speaker has been on a mission to bring down Romney since the Iowa caucuses on Jan. 3. He blamed the Romney campaign for a series of negative ads against him that caused his support to wither in the state.

But attack ads about Romney's tenure as head of Bain Capital, portraying him as a ruthless corporate raider, didn't do any serious damage to the front-runner in South Carolina.

Instead, it's his waffling on tax returns that appears to be hurting him.

Nonetheless, Romney's still got a commanding lead in Florida, the site of the race's next contest. But by late in the day Friday, his campaign still hadn't committed to his participation in an NBC debate on Monday night in Tampa, possibly because the two South Carolina showdowns have caused him such trouble.

Meantime, allegations from Gingrich's second wife just two days before the primary were still resonating.

Marianne Gingrich claims her ex-husband wanted her to participate in an "open marriage" that would allow him to continue carrying on with his extra-marital girlfriend, Callista Bisek.

Marianne Gingrich also claimed that her ex carried on his affair with Bisek for six years, frequently bedding the congressional aide in their marital bed at the couple's Washington, D.C., apartment. Gingrich had left his first wife, Jackie, for Marianne 18 years earlier.

Marianne Gingrich says she refused his request for an open marriage; Gingrich later married his mistress, now the third Mrs. Gingrich.

Gingrich spewed vitriol at CNN's John King in Thursday night's debate when he asked about the allegations, denying them vehemently while calling him "despicable" for asking the question. The crowd roared its approval, giving him one of a handful of standing ovations.