WASHINGTON (AP) - Newt Gingrich worked to capitalize Sunday on his upset victory in South Carolina's Republican presidential primary, while Mitt Romney moved quickly to cut his losses before the next contest with a promise to release his income tax returns within 48 hours.
Gingrich said in a round of television interviews that his win, both unexpected and unexpectedly large, showed he was the Republican best able to go toe to toe with President Barack Obama in the fall.
"I think virtually everybody who looks at the campaign knows I represent the largest amount of change of any candidate, and I think that's why they see me as representing their interest and their concerns, not representing Wall Street or representing the politicians of Washington," he said.
Romney argued that point, but not another, agreeing in a television interview that he had made a mistake by refusing to release his tax returns before the South Carolina vote.
"If it was a distraction, we want to get back to the real issues in the campaign -- leadership, character and vision for America, how to get jobs in America, and how to rein in the excessive scale of the federal government," he said.
The former Massachusetts governor, who made millions in business, said he will make his 2010 return and an estimate for 2011 available online on Tuesday.
The decision marked a concession, as if one were needed, that Romney had stumbled on his way through South Carolina, a state where he led handsomely in the polls several days before the primary.
Florida votes next, on Jan. 31, a 50-delegate contest in one of the most expensive campaign states in the country, and one that Romney can ill afford to lose.
The former governor was an easy winner in the New Hampshire primary earlier in the month. Before that, he was a close runner-up behind former Pennsylvania Sen. Rick Santorum in Iowa caucuses where the vote count was so confused that he was originally announced the victor.
Despite his loss on Saturday, Romney remains the contender with the largest and best-funded organization.
"Three states in now, we got 47 more to go," he said, adding he was looking forward to the rest.
For all the political momentum gained in South Carolina, Gingrich made it immediately obvious that he is short on funds. He urged supporters via Tweet Saturday night to donate money, and then announced the name of his campaign website while making a nationally televised victory speech.
With their comments, both Romney and Gingrich indicated the race was a two-way competition, likely to go into the spring if not longer.
Santorum had other ideas.
"We're going to Florida and beyond," he said. As he did in a pair of debates in South Carolina, he criticized both Gingrich - calling him a "very high-risk candidate" - and Romney, whom he called a moderate ill-suited to appeal to conservative voters.
Texas Rep. Ron Paul, the fourth contender, has already said he will skip Florida and focus on Nevada and other caucus states.
Gingrich won South Carolina despite being outspent. But in addition to the prohibitive cost of campaigning in Florida, a long-term shortage of funds can cripple efforts to compete in the fast-paced series of primaries and caucuses ahead.
Aides say the former speaker raised $9 million in the final quarter of 2011.
Romney has reported taking in $24 million over the same period.
In addition, both men are supported by outside groups that have paid for millions in television advertising. So far, though, Romney's has spent more, and to greater evident effect.
When Gingrich surged in the polls two weeks before the Iowa caucuses, Restore Our Future responded with hard-hitting ads that knocked the former speaker off-stride and protected Romney's standing.
Gingrich lacked the funds to respond effectively, lashed out angrily, and sank to a poor fourth place finish. He did not begin to recover until the final days of the race in South Carolina, when he was aided by Romney's missteps, Texas Gov. Rick Perry's mid-week withdrawal and endorsement, and his own strong debate performances.
Also in the interim, Gingrich supporters said that casino magnate Sheldon Adelson had written a $5 million check to an outside group set up to help the former speaker.
Allies of Gingrich have made no secret of their hope that Adelson will help again in Florida, where the pro-Romney organization shows no signs of slowing down.
Even before the polls closed in South Carolina, Romney and a group supporting him had spent $7 million on television advertising in Florida. So far, the only other political ads to run in the state were financed by ASCME, a labor union working to weaken the standing of the former Massachusetts governor.
While a protracted battle for the nomination could benefit Obama, the signs pointed toward a particularly bruising struggle in Florida.
"I don't think that the people of this country are going to choose as the next president of the United States a person who spent 40 years in Washington as a congressman and a lobbyist," Romney said. "That is not going to be, in my opinion, be the most effective way to replace the current president who also spent his career in politics."
"I think South Carolinians were the first state to really understand how liberal Governor Romney's record was" as Massachusetts governor, said Gingrich.
He said his main rival lost ground "as people began to realize that he'd been pro-choice, pro-gun control, pro-tax increase in a whole range of areas that despite his advertising and his pretending, it was clear that he was way to the left of South Carolinians."
With votes counted from all of South Carolina's precincts, Gingrich had 40 percent to Romney's 28 percent. Santorum won 17 percent to Paul's 13 percent.
Gingrich won at least 23 of the 25 delegates at stake. The other two have yet to be allocated.
Gingrich appeared on NBC's "Meet the Press," CBS' "Face the Nation" and CNN's "State of the Union." Romney was on "Fox News Sunday," while Santorum was on ABC's "This Week" and CNN.