Suddenly 'Neck and Neck' _ Romney, Gingrich in SC On the eve of a Southern showdown, Mitt Romney conceded Friday he's in a tight race with Newt Gingrich for Saturday's South Carolina primary in a Republican campaign suddenly turned turbulent. It's "neck and neck," Romney declared, then said later in the day he expects he will win some states while Gingrich takes others in the primaries and caucuses ahead. Former Sen. Rick Santorum, swiped at both men in hopes of springing a South Carolina surprise. But several days after forecasting a Romney victory in his state, Sen. Jim DeMint said the campaign's first Southern primary was now a two-man race between the former Massachusetts governor, who has struggled in recent days with questions about his personal wealth and taxes, and Gingrich, the former House speaker who has been surging in polls after a pair of well-received debate performances. The stakes were high as Republicans sought a challenger to Democratic President Barack Obama. Television advertising by the candidates and their supporters exceeded $10 million here, much of it spent in the past two weeks, and mailboxes were stuffed with campaign flyers. In a bit of home-state boosterism, DeMint said the primary winner was "likely to be the next president of the United States." Indeed, the winner of the state's primary has gone on to capture the Republican nomination each year since 1980. FILE - In this Jan. 7, 1997 photo, House Speaker Newt Gingrich of Georgia and his wife Marianne leave their home for Capitol Hill. Dredging up a past that Newt Gingrich has worked hard to bury, the GOP presidential candidate's ex-wife says Gingrich asked for an "open marriage" in which he could have both a wife and a mistress. In an interview with ABC News' "Nightline" scheduled to air Thursday, Jan. 19, 2012, Marianne Gingrich said she refused to go along with the proposal that she share her husband with Callista Bisek, who would later become his third wife. (AP Photo/Mark Wilson) Close A victory by Romney would place him in a commanding position heading into the Florida primary on Jan. 31. He and an organization supporting him are already airing television ads in that state, which is one of the country's costliest in which to campaign. If the former Massachusetts governor stumbles in South Carolina - as senior aides conceded he might - it could portend a long, drawn-out battle for the nomination stretching well into spring and further expose rifts inside the party between those who want a candidate who can defeat Obama more than anything else, and those whose strong preference is for a solid conservative. Romney sounded anything but confident as he told reporters that in South Carolina, "I realize that I had a lot of ground to make up and Speaker Gingrich is from a neighboring state, well known, popular ... and frankly to be in a neck-and-neck race at this last moment is kind of exciting." Left unspoken was that he swept into South Carolina 10 days ago on the strength of a strong victory in the New Hampshire primary and maintained a double-digit lead in the South Carolina polls for much of the week. Campaigning in Gilbert, S.C., on Friday, Romney demanded that Gingrich release hundreds of supporting documents relating to an ethics committee investigation into his activities while he was speaker of the House in the mid-1990s. ""Of course he should," he told reporters. Referring to the House Democratic leader, he said, "Nancy Pelosi has the full record of that ethics investigation. You know it's going to get out ahead of the general election. That was an attempt to turn the tables on Gingrich, who has demanded Romney release his income tax returns before the weekend primary so Republicans can know in advance if they contain anything that could compromise the party's chances against Obama this fall. Gingrich's campaign brushed off Romney's demand, calling it a "panic attack" brought on by sinking poll numbers.