Charleston, South Carolina (CNN) -- The four remaining Republican presidential candidates faced off Thursday for the second time in three days and two days ahead of South Carolina's pivotal primary.
Just weeks ago, South Carolina looked like it might seal the deal for then-front-runner Mitt Romney, but the polls have tightened in the weeks leading up to Saturday's vote.
Here are five things we learned from the CNN-Southern Republican debate:
Newt nails the press... again
It took less than five minutes for Newt Gingrich to find his sweet spot.
In the first question of the debate, moderator John King asked Gingrich if he wanted to respond to the drama that engulfed his campaign on Thursday -- the claim by ex-wife, Marianne, that the former House speaker asked her to have an "open marriage" while he was having an affair with a staffer (his current wife, Callista).
Gingrich glowered at King and responded: "No."
He proceeded to fume at CNN and the rest of the media for their "despicable" efforts to peddle "trash" just days before the pivotal South Carolina primary -- a lengthy tirade that drew cheers and a standing ovation from the audience in North Charleston.
"I am tired of the elite media protecting Barack Obama by attacking Republicans," he said, once again embracing his self-appointed role as the GOP's leading media critic.
There was also a new headline buried beneath the fireworks: Gingrich denied Marianne's charges outright, something he had stopped short of doing in the wake of Marianne Gingrich's explosive ABC News interview.
Never mind that character or personality issues are fixtures of American political campaigns -- or that Gingrich helped lead the charge against President Bill Clinton after he admitted infidelity with a White House intern in 1998 -- his press-bashing tirade was largely a winning tactic.
Gingrich curried favor with Republicans and neutralized the sting of the ABC story by painting the media as a bunch of salacious liberal muckrakers.
At the end of the night, though, his indignation had miraculously subsided.
Given the chance to make a closing statement, Gingrich politely thanked CNN for an "interesting and useful evening."
Character issues are fair game
While his pushback against the "open marriage" question was aggressive, Gingrich did not completely sideline the issue of his past infidelities -- a topic that frequently bubbles up across South Carolina in conversations with Republican voters.
Gingrich's two main rivals for the conservative anti-Romney vote -- Santorum and Ron Paul -- both said questions about a candidate's character were fair game.
"These are issues of our lives and what we did in our lives," said Santorum, a staunch Catholic who has made faith and values central themes of his candidacy. "They are issues of character for people to consider. But the bottom line is those are -- those are things for everyone in this audience to look at. And they're going to look at me, look at what I've done in my private life and personal life, unfortunately."
Paul said Republicans face unfair scrutiny from the media, but agreed with Santorum.
"I think setting standards are very important and I'm very proud that my wife of 54 years is with me tonight," he said.
Only Romney, who prefers to talk about the economy, took a pass on the character issue.
"Let's get on to the real issues is all I've got to say," he said.
Taxes take center stage
For the second time in one week, Romney hit a speed bump when pressed on the matter of his tax returns.
Asked by Rick Perry and moderators during a debate in Myrtle Beach on Monday if he plans to publicly release his tax records, Romney squirmed and said he might release them sometime around April.
He gave a more definitive answer the following day on the campaign trail to clean up the mess, promising to release his returns and revealing that he probably pays a 15% tax rate -- a rate lower than many working Americans pay.
King asked Romney on Thursday if he would follow the example of his father, George Romney, -- also a governor and presidential candidate -- who made his tax returns public for 12 years.
"Maybe," he said. "I don't know how many years I'll release."
Romney's hesitant answer was jeered by the crowd.
Gingrich -- who posted his own tax returns online just as the debate began -- pounced on Romney's equivocation.
"If there's anything in there that is going to help us lose the election, we should know it before the nomination," he said. "And if there's nothing in there -- if there's nothing in there, why not release it?
Romney eventually found his footing toward the end of his answer when he said he anticipated attacks from Democrats about his enormous personal wealth, estimated to be somewhere between $190 million and $250 million.
"I know the Democrats want to go after the fact that I've been successful," he said forcefully. "I'm not going to apologize for being successful."
Santorum stops the bleeding
Santorum has proven himself a skilled debater throughout the Republican race -- and he showed it once again Thursday when he needed it most.
With Jon Huntsman and Rick Perry now out of the race, the field of Republican contenders is now down to four. Santorum took advantage of the extra speaking time and framed himself as the conservative alternative to Romney and Gingrich.
When Romney and Gingrich sparred over hot-button topics like illegal immigration and health care reform, Santorum calmly explained each of his rival's heresies on those very issues and positioned himself to their right.
Santorum also delivered the sharpest and most detailed takedown to date of Gingrich's rocky tenure as Speaker of the House.
"Four years into his speakership, he was thrown out by the conservatives," Santorum said. "It was a coup against him in three. I served with him. I was there. I knew what the problems were going on in the House of Representatives when Newt Gingrich was leading this -- leading there. It was an idea a minute, no discipline, no ability to be able to pull things together."
With polls showing the South Carolina race quickly transforming into a two-man between Romney and Gingrich, Santorum needed a strong night to stop the bleeding.
Even rival campaigns acknowledged in the post-debate spin room that Santorum scored big.
The real winner: 'Grandiosity'
One of Santorum's best lines was a swipe at Gingrich's reputation for pomposity and disorganization.
"Grandiosity has never been a problem with Newt Gingrich," Santorum said. "He handles it very, very well."
Gingrich, who has never met an argument he didn't try to win, tried to turn the charge into a positive.
"You're right," he responded. "I think grandiose thoughts. This is a grandiose country of big people doing big things. And we need leadership prepared to take on big projects."
The Romney campaign, which has worked to convince voters that Gingrich lacks the discipline to be president, took the opportunity to blast out one of the most entertaining news releases the 2012 election cycle -- a compilation of Gingrich making over-the-top statements about himself.
Some of his greatest hits:
"I am essentially a revolutionary," he told The New York Times in 1992.
"I have an enormous personal ambition," Gingrich said to the Washington Post in 1985. "I want to shift the entire planet. And I'm doing it ... I represent real power."
Or this gem, from a debate last year: "I am the longest-serving teacher in the senior military, 23 years teaching one and two-star generals and admirals the art of war."
And so on.
The Romney release also noted that Gingrich has, in the past, compared himself to historical figures like Pericles, William Wallace, Charles De Gaulle, Abraham Lincoln, Vince Lombardi and Moses.