COLUMBIA, S.C. — Mitt Romney blew a double-digit lead in South Carolina after two weak debate performances where he struggled to deliver a cogent response to questions about his tax returns.

It was a long fall for the former Massachusetts governor, who earlier this week was the winner of the first two early-voting states, leading his presidential rivals in South Carolina by double digits, and considered to have locked up the Republican nomination.

But, on Saturday, he lost South Carolina to Newt Gingrich. With 99 percent of precincts reporting, Gingrich had 41 percent to Romney's 27 percent.

"This race is getting to be even more interesting," Romney said Saturday at his election night rally, emphasizing, "We've still got a long way to go."

One state doesn't decide the nomination — despite South Carolina's history of picking the winner since its primary began in 1980.

In Florida, the next state to vote, Romney holds a double digit lead in the polls. He's the only candidate on the air in the expensive media market. He also has a much superior ground game than Gingrich.

But waiting for Romney there are two more debates: events in which Gingrich excels and Romney struggles.

They were part of his downfall in South Carolina as he stumbled when asked about his tax returns, an issue his rivals successfully hammered him on.

At Monday’s debate, Romney hemmed and hawed about releasing his returns, only committing to saying he would “probably” put them out in April. On Thursday, when given another chance on the question and asked if he’d release 12 years of tax returns like his father, former Michigan Gov. George Romney (R) did during his presidential run, he seemed ill-prepared once again.

“Maybe," Romney said, laughing. "I'll release multiple years. I don't know how many years."

Many in the crowd booed and jeered.

The former governor spent much of his time in the state on the defensive, struggling to put to rest the questions about his tax returns and personal fortune.

David Woodard, a top GOP strategist and Clemson professor who has regularly polled the race, said Gingrich's Monday debate performance was more important than any missteps Romney had made.

"Tuesday night was the first night I began to see there was a real change," he said. "That was the day the press was saying Gingrich was surging. On Wednesday night the roof fell in. We’d been polling for an hour and hadn’t heard a Romney answer yet, and we just junked everything we’d done before."

But Woodard said Romney hadn't helped himself any with his debate performances. "If you’re worth a quarter billion dollars, that's the one thing that everyone’s going to ask about. It seems like you should have a defense prepared right away.

"There’s this latent anger and resentment and Gingrich was able to tap into that. There’s nothing angry about Mitt Romney... When you kind of have that pent up frustration Gingrich taps it, Romney does not."

Romney also gave his opponents ammunition to argue that he was an out-of-touch elitist.  When pressed on his taxes, he said his tax rate was around 15 percent, much lower than most Americans, and that the $375,000 he made in speaking fees last year was “not very much.”

That argument was especially dangerous in South Carolina, a largely blue-collar state with a 9.9 percent unemployment rate, one of the highest in the country.

And he was hurt by a report from ABC News that noted he had millions in investment funds based in the Cayman Islands and questioned whether the former governor had put the money there to further avoid tax liabilities. The campaign dismissed the report as “flat wrong” and insisted that Romney paid the same taxes on those investments as he would in the United States. But the story played into the wider narrative that dragged him down.

Romney strategists have told The Hill in the past that the former governor is a much better candidate when he is “not afraid to lose,” as one put it. When he is trying to hold a lead, he becomes defensive and tightens up, and that results in him making mistakes and coming off as awkward. That tendency was on display this week, when Romney saw his lead evaporate.

But there were some factors out of Romney's control.

On Thursday, the Iowa Republican Party declared that Rick Santorum had actually won their caucuses by 34 votes. It had previously called the race a tie, and unofficial results had put Romney as the winner by eight votes.

The same day, Rick Perry dropped out of the race and endorsed Gingrich.

Gingrich’s rise was another thing Romney couldn’t stop. The former Speaker had two strong debates this week and exit polls showed voters citing those debates as part of their decision-making process.

He delighted voters in Thursday night's debate, when he hammered the media for asking about his relationship with his second wife and fired zingers at President Obama -- all of which earned him applause, and even a standing ovation, from the crowd.

Perry's endorsement gave Gingrich an additional boost and made it clear to voters that he, not Rick Santorum, was the choice for those who wanted to stop a Romney coronation.

But politics is about momentum and expectations as much as outcomes, and the results reflected not only a Gingrich surge but a Romney slide. The former governor was as high as 37 percent in one mid-week poll, but finished with 27 percent, according to early returns. That showed that he not only hit his ceiling in the state, but bounced off of it.

Romney advisors argue that South Carolina was always going to be a tough state for them and point out that, in 2008, the former governor finished in fourth place with 15 percent. Voters tend to be social conservatives and Tea Partiers, the two groups most resistant to Romney. In the state, like Iowa before it, approximately 60 percent of GOP primary voters are evangelical Christians.

Romney’s campaign schedule was also puzzling. In the closing days of the campaign he spent as much time in upstate South Carolina, an area filled with social conservatives, rather than focusing on driving up the vote along the coast, where there are many suburban voters, retirees from the northeast and military voters — people who might have been more easily swayed to vote for him.

At some upstate events in the closing days, Romney’s campaign was forced to flesh out the crowds with supporters who had come down from Virginia to help with the campaign.

One event was particularly embarrassing for Romney. His staff announced that he would appear at the Tommy’s Country Ham House in Greenville on Saturday without checking with the restaurant’s owner; Gingrich’s campaign had scheduled a stop at the exact same time. Gingrich offered to debate Romney but the former governor declined.

After saying he would not change the time on Friday night, Romney backed down, showing up an hour early on Saturday to avoid Gingrich and rushing out of the restaurant quickly.

Romney’s maneuver showed weakness, and gave Gingrich a chance to take a shot at him.

“I have a question — where’s Mitt? I thought he was going to stay and maybe we’d have a little debate here this morning,” the former Speaker said as the crowd cheered and a few supporters made clucking chicken noises.

And Romney’s surrogates may have hurt him more than they helped. South Carolina Gov. Nikki Haley (R) predicted on several occasions that Romney would win the state, keeping that line even after polls showed Gingrich with an increasingly large lead.

When asked if Haley had hurt the Romney campaign by predicting a win in the Palmetto State, a Romney staffer grinned wryly and said “It’s good to have friends on your side who are optimistic.”

Virginia Gov. Bob McDonnell (R), who came down to endorse Romney on Friday, joked at one event that "I think there's 100 people here from Virginia,” drawing attention to the fact that many of those out for Romney were not locals.

Romney previewed the attack lines he'll likely use against Gingrich in Florida in his remarks at his election night rally Saturday.

“We cannot defeat the president with a candidate who has joined that very assault on free enterprise,” he said. “When my opponents attack success and free enterprise… they’re attacking you.”

He added: "Our party can't be led to victory by someone who has never run a business and never led a state."

He never mentioned Gingrich by name in his attacks but it was obvious who they were directed at.

"Our campaign will about the businesses I helped start, not the bills I tried to pass," the former governor said.

"We're going to win this nomination and we're going to defeat President Obama in November."

-- This story was updated at 10:36 p.m.