On the morning after a bellicose debate performance that had the audience leaping to its feet, Newt Gingrich got this challenge from a retired Marine officer who had come to hear him speak at an art gallery here.

“What I’ve been looking for in my candidate is, we’ve got to bloody Obama’s nose,” Vence Jelovchan said.

“I don’t want to bloody his nose,” the former House speaker replied. “I want to knock him out.”

There is much on the line for Gingrich in South Carolina. Saturday’s GOP primary could spell the end of his presidential hopes — and with them, a political career that has helped shape Republican politics for more than three decades.

So, with the stakes that high, Gingrich has returned to his roots.

To hear him these days on the stump is to recall the back-bencher he once was in the House of Representatives, when he first emerged as the anti-establishment warrior of late-night C-SPAN. As he did then, Gingrich swings vigorously at the welfare state, political correctness, liberal orthodoxy and whatever opponent is standing in his way.

It seems to be working. Since the debate Monday night, his crowds have been growing, as has their enthusiasm. Tea party icon and former Alaska governor Sarah Palin has said she would vote for him if she lived in South Carolina, and talk radio is abuzz. And another debate is scheduled for Thursday night.

Everywhere he goes, conservatives appear to be remembering what it was they liked about Gingrich in the first place.

While former Massachusetts governor Mitt Romney remains in the lead here, a Time-CNN poll — conducted largely before what Gingrich described as “the best debate I’ve had this year” on Monday night — indicated that Gingrich is closing the gap.

In less than two weeks, the margin between the two in South Carolina has shrunk by almost half, to 10 points.

“I’m back,” Gingrich exulted Wednesday in an interview.

Still, a Gingrich upset here remains a tall order for a candidate who did not place better than fourth in either of the previous contests, in Iowa and New Hampshire.

A win would also represent a repudiation of South Carolina’s reputation as a killing field for political insurgents. In every GOP primary race since the state took its prominent place on the campaign calendar 32 years ago, South Carolina has voted for the establishment favorite and sent him on his way to the nomination.

This year, that would be Romney, who in addition to having superior resources and organization has benefited from the fact that the conservative vote opposing his candidacy has been splintered among Gingrich, former senator Rick Santorum (Pa.) and Texas Gov. Rick Perry. Meanwhile, Rep. Ron Paul (Tex.) maintains a loyal and energetic libertarian following.

In the few days that remain, “We have to finish getting votes away from Santorum and Perry, and we have to erode Romney a little more,” Gingrich said. “I think we can do it.”

And how will he do it?

“You do it by the debates,” he said.

His, however, has been a campaign that has taken on many personalities and has had more than its share of ups and downs. It all but collapsed shortly after it began last summer.

But Gingrich rehabilitated himself by assuming the upbeat role of an elder statesman in the early debates. Then, when he surged in the polls, he grew overconfident and stumbled into an onslaught of negative advertising from Romney’s allies. So he abandoned his pledge to stay positive and counterattacked.

One of the biggest signs that things may be turning Gingrich’s way again is the renewed attention he has been getting from the front-runner.

On Wednesday, Romney’s campaign organized a conference call in which two of Gingrich’s former Republican congressional colleagues, Jim Talent (Mo.) and Susan Molinari (N.Y.), recounted the turbulence of his time as speaker of the House. In a tough new television ad, they call him “an unreliable leader.”

“It was leadership by chaos,” Molinari said.

And Romney, in a departure from his usual strategy of focusing his stump speech on President Obama, scoffed at Gingrich’s boast that he helped create jobs while he was in Congress.

“Government doesn’t create jobs,” Romney said. “It’s the private sector that creates jobs. Congressmen taking responsibility or taking credit for helping create jobs is like Al Gore taking credit for the Internet.”

Speaking Wednesday to an overflow crowd at a barbecue restaurant in Warrenville, Gingrich predicted that the final days before the primary will be brutal.

“I think they will be unendingly dirty and dishonest for the next four days, because they’re desperate. They thought they could buy this,” he said of Romney’s campaign.

To gain any real traction against Romney, Gingrich’s strategists say, the former House speaker must establish himself in voters’ minds as a more credible threat to the president.

Exit polls conducted during the New Hampshire primary showed that for more than one-third of those voters, the top priority was coming up with a nominee who could beat Obama.

And among that group — which was larger than the one in which respondents said they most valued conservatism, experience or character — Romney was beating Gingrich by better than 5 to 1.

So at every stop in South Carolina, Gingrich warns about the dangers of nominating “a moderate from Massachusetts” who used to support abortion rights and who put into place a state health-care system that looks similar to the new federal law that all the GOP candidates have vowed to repeal.

“If you are serious about beating Obama, you need somebody who knows what they are doing; you need somebody who can articulate it clearly; and you need somebody who is prepared to go toe to toe with Obama,” Gingrich said Tuesday night at an Aiken County Republican Party rally. “The debate between Romneycare and Obamacare is going to be very confusing.”

Gingrich also is not backing off his attacks on Romney’s record leading the private equity firm Bain Capital — although Gingrich’s strategists concede that he may have hurt himself in the short run. Other Republicans have complained that he is echoing the anti-business attacks of Democrats and Occupy Wall Street protesters.

“Raising a question about a particular person and a particular company who has made that one of his two major claims running for president is hardly an attack on capitalism,” Gingrich said at a South Carolina Chamber of Commerce forum. “The Bain model is to go in at a very low price, borrow an immense amount of money, pay Bain a great deal of money and leave. I’ll let you decide if that’s really good capitalism. I think it’s exploitive. I think it’s not defensible.”

Gingrich is not mincing words, but with only two days to go before a make-or-break election, he doesn’t have time to.