Tonight, the Republican presidential candidates will gather in Charleston, S.C., for one final debate before the South Carolina primary on Saturday. With Rick Perry out of the race, there will be just four of them: Newt Gingrich, Ron Paul, Mitt Romney and Rick Santorum.

The last debate took place on Monday in Myrtle Beach, S.C. Gingrich won by most accounts, and in the three days since, he has gone from trailing Romney by 10 percentage points to beating him in two polls released Thursday -- as if to demonstrate that debates are still important, even in a campaign that has already endured more than a dozen of them.

Romney performed respectably in that debate, but Gingrich gave the most impassioned responses and received the most enthusiastic reactions from the audience. Romney will be hoping to make a better impression tonight.

Meanwhile, Santorum will be making a last-ditch attempt to salvage the momentum he had coming out of Iowa. That momentum has faded along with his poll numbers in South Carolina, in spite of the news that he, not Romney, had actually won the Iowa caucuses on Jan. 3. He has fallen into fourth place behind Paul in the latest polls of South Carolina voters, and if he places last in a socially conservative state where 60 percent of the Republican electorate is evangelical, it will be difficult if not impossible for him to keep going.

Paul is not focusing on South Carolina as much as he is on upcoming caucus states like Nevada, but he will nonetheless be hoping to do better tonight than he did on Monday, when the audience booed his arguments for cutting military spending.

The International Business Times will be live-blogging the debate on this page starting at 8 p.m. EST, and be sure to check back afterward for post-debate analysis.

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9:59 p.m.: That's the end of the debate. Check back later for analysis of who won and what it means for Saturday's primary.

9:58 p.m.: Santorum adds that South Carolina, like other states, has long been told it should vote for an electable moderate, but back in 1980, it rejected that argument and chose Ronald Reagan over George H.W. Bush. You voted for Reagan before Reagan was the Reagan we knew, he says.

9:56 p.m.: Santorum says he agrees with Romney on what's at stake in this election, but the best person to challenge Obama is someone who presents a clear contrast on the most important issues: health care, global warming, the bailouts, etc. We need someone who has a track record of conservatism, not just someone who is conservative now. He also notes that he is the only person onstage who has defeated a Democratic incumbent, and the only one who has won an election in a swing state.

9:55 p.m.: Obama is changing the very nature of America, Romney says. He's making us an entitlement society, where people think they're entitled to what other people have. ... That has never been the source of American greatness. Obama has said he wants to fundamentally transform America, but what we really need to do is restore America to the values that made it the hope of the earth, and he, Romney, is the only one who understands those values, he says.

9:53 p.m.: Gingrich calls Obama the most dangerous president in history and says it is imperative to beat him -- but also to take back the Senate and keep control of the House. A Saul Alinsky radical who is incompetent cannot be re-elected, he says.

9:51 p.m.: Paul's case to South Carolina: it is known for its respect for liberty. Lots of people talk about what candidates would do for particular states, but if you understand liberty, it's equal for everybody, it benefits everybody. He also mentions his commitment to reducing the federal budget and the federal debt. We have to be willing to look at overseas spending and all of the entitlement spending here in this country.

9:47 p.m.: Last commercial break of the night. One moment of levity in Paul's response just now: after the first part of it, Santorum chimed in with a rebuttal because he assumed Paul was attacking him obliquely. When it was Paul's turn to speak again, he told Santorum he hadn't even been thinking about him, and that he was being overly sensitive. Huge applause from the audience.

9:46 p.m.: Santorum retorts that Paul's right-to-life record in Congress is less than 60 percent, which is about the same as Harry Reid's. He says Paul can't call himself pro-life when he votes against congressional legislation to protect life -- life, Santorum says, is a federal issue, not a state issue. Paul responds: I see abortion as a violent act. All other violent action is handled by the states, so don't try to say that I'm less pro-life because I want to be particular about the way we do it.

9:43 p.m.: King is about to move on, but the audience starts shouting Paul's name, so King gives him a chance to weigh in. He says that as a doctor, when caring for pregnant women, he always saw it as having two patients, because life begins at conception. He adds that law follows morality, and so in order to ensure pro-life laws, we have to change the mentality of the American people.

9:42 p.m.: Romney responds that he was governor in a state where being pro-life was not easy. He says he did veto several pieces of legislation that would have expanded abortion rights and stem-cell research, and he pushed for abstinence-based sex education against the opposition of Democratic legislators. He did the best he could to be a pro-life governor, he says, and he would be a pro-life president.

9:40 p.m.: Santorum says it was Romney's responsibility to include a provision in the Massachusetts health care law that specifically prohibited funding for abortions, because he should have known that if he left it unspecified, the courts would rule that abortion had to be covered. He then accuses candidates like Romney of whispering that they are pro-life, while other people -- that is, himself -- fought the battles.

9:39 p.m.: Romney responds that the Massachusetts health care law said nothing about abortion; it was a state judge who ruled that coverage had to include abortions. He would have vetoed any law that authorized funding for abortion, he said. He adds, on the question of judges, that he did not have a litmus test as governor for the criminal judges he appointed.

9:36 p.m.: Gingrich accuses Romneycare of funding abortions. He also accuses Romney of appointing pro-choice judges even after his described conversion to being pro-life.

9:35 p.m.: Paul adds: Why don't we take our resources away from foreign borders, like the India-Pakistan border, and dedicate them to protecting our own border?

9:34 p.m.: Paul says the best way to combat illegal immigration is through incentives and disincentives. He says individuals who hire illegal immigrants, say to clean their homes, shouldn't be punished, because it should be law enforcement officials enforcing our laws, not individuals enforcing those laws.

9:32 p.m.: Romney emphasizes that the Republican Party is a party of legal immigration, and in order to support legal immigration, we have to oppose illegal immigration.

9:31 p.m.: Santorum says, yes, it's hard to separate people from their families when they've been here for decades, but we can't accept people coming here and, with their first act, breaking our laws. He adds that it's not just one instance of law-breaking -- if they've been working in the country for 25 years, they've been breaking the law constantly for 25 years.

9:29 p.m.: Romney says there are a lot of difficult problems to solve in this country, but illegal immigration isn't one of them -- we just need to build a fence and punish companies that hire illegal immigrants. He doesn't believe in deporting every last illegal immigrant, but there should be no advantage toward permanent residency or citizenship for people who cut in line.

9:27 p.m.: Gingrich stands by his previous position that, while most illegal immigrants would leave voluntarily if we implemented policies that made life difficult for them, we can't deport every person who's been here for decades and has family here. Trying to deport grandmothers and grandfathers would never pass Congress and would never be accepted by the American people, he says.

9:25 p.m.: The latest audience question is about how the candidates would prevent illegal immigrants from taking American jobs. Gingrich is up first: You have to first of all control the border, he says, pledging to do that by 2014. He also advocates English as the official national language -- a proposal that gets a lot of applause. Third, he would expedite the process of legal immigration, and fourth, he would make it much easier to deport people. ... We should be able to get rid of you in two weeks, not two years.

9:22 p.m.: I wouldn't change a thing, Santorum says. He could never have imagined being in the final four given how completely he was ignored at the beginning of the race. It proved that good ideas and hard work still pay off in America, he says. Paul says he can't think of one thing, but he would like to be a better deliverer of a message by... speaking slower?

9:21 p.m.: Gingrich says, in response to the question posed before the break, that he would skip the first three months in which he hired traditional consultants, and go straight to presenting big ideas. Romney jokes that he would try to get 25 more votes in Iowa. (Santorum shrugs.) Romney would also take back all the time he's spent talking about his Republican opponents and spend it talking about Obama, because Obama is in way over his head and is taking the country down a dangerous road toward European socialism. Any of the people onstage, he says, would be better than Obama.

9:16 p.m.: Commercial break. Up next: if the candidates could do one thing over in this campaign, what would it be?

9:15 p.m.: Paul notes that he was one of the first people to come out against SOPA, and he says he is pleased with Romney's and Gingrich's responses because Republicans are all too often on the wrong side of this issue. Then it's Santorum's turn: he, too, opposes SOPA, but he does not agree that the government has no right to step in when foreign Web sites are pirating Americans' intellectual property.

9:13 p.m.: Gingrich explains why he opposes SOPA. He says patent laws already allow companies with legitimate claims of infringement to sue over them, but there is no need for a preemptive federal law. Romney agrees: The law as written is far too intrusive, far too expansive, and would depress one of the fastest-growing industries in America, the internet. He says he would support a narrower law to combat piracy, but he cannot support a law as broad as SOPA.

9:11 p.m.: Santorum says that when his state voted against right-to-work laws, he wasn't going to overrule it from the federal level. Paul asks if, as president, he would represent Pennsylvania or South Carolina. Santorum makes a face and says maybe Paul didn't hear him: as president, yes, he would support a national right-to-work law.

9:10 p.m.: Paul says preventing outsourcing is about creating the right conditions in the U.S. We shouldn't be frightened about trade ... but we have to look at the reason why we're doing this, he says. He adds, Believe me, the regulations and the fact that we are the issuer of the Reserve currency of the world are going to backfire.

9:07 p.m.: Santorum also touts his plan to let international corporations bring overseas profits back to the U.S. without paying taxes on those profits, so long as they invest them in jobs. It's worth noting, though, that he's not the only candidate who has suggested that.

9:06 p.m.: Here's another audience question: Apple employs about 46,000 people in the United States, but 500,000 in China. How would Santorum prevent that sort of outsourcing? Santorum says he's the only candidate onstage who would prevent that, because his plan to eliminate taxes on manufacturers would create a big incentive for companies to return to the U.S. Outsourcing is all about government getting in the way, he says.

9:05 p.m.: King asks Romney whether he'll release more than one year of his tax returns, since a single year can be misleading or unrepresentative. Romney says maybe. The audience doesn't like that at all. But when he says he's not going to apologize for being successful because I worked hard in the American way, the audience is immediately back with him, applauding.

9:03 p.m.: Santorum says he'll release his taxes as soon as he gets home, because he does his own taxes and they're on his computer and he can't get them until he's home. He says he can assure voters that his effective tax rate is higher than Romney's, adding that it's painful writing the checks, but he doesn't know exactly what his rate is.

9:01 p.m.: An audience member asks the candidates when they're going to release their tax returns. Gingrich jokes, An hour ago. Paul says he has no intention of doing so, adding that his finances are an open book based on his congressional disclosures. Romney says he will release his once his 2011 tax returns are complete, and then takes a minute to say that Obama attacks people who have been successful.

8:59 p.m.: Gingrich responds that when he became speaker in the 1990s, he brought the government back around to the Reagan model. He says Romney succeeded in the private sector as a result of the policies Gingrich worked on as speaker. Romney retorts that Gingrich was speaker of the House for four years, while Romney was a businessman for 25 years, so you're not going to take credit for my 25 years. He adds that, as a businessman, he was never thankful for what Washington did for him -- he just wanted Washington out of the way.

8:58 p.m.: Gingrich spent a lot of his time talking about everything he accomplished with Ronald Reagan, but, Romney says, he is only mentioned once in Reagan's diaries, and it was for having an idea that Reagan didn't like and rejected.

8:57 p.m.: What you just heard, Romney says -- that whole exchange between Gingrich and Santorum -- is a prime example of why we need to elect a president who has not spent his life in Washington. Everyone else onstage, he says, is a Washington insider. Then he takes that back, noting that Paul spent most of his career in the birthing suite. Applause, and one audience member screams, YEAH!

8:55 p.m.: And Gingrich is back to listing his accomplishments in Congress, focusing on the things he did that went against Republican leadership. By the time Santorum was first elected to the Senate, he says, Gingrich already had a reputation as a principled rebel. Those are just historical facts, even if they're inconvenient for Rick's campaign, he says.

8:53 p.m.: Santorum says he'll grant that Gingrich has big ideas, but he says he can't execute them. He notes that he served with Gingrich in Congress, and it was an idea a minute, and Gingrich didn't have the discipline to put those ideas into practice. Applause.

8:52 p.m.: King asks Gingrich what, exactly, he meant when he said Santorum didn't have any of the knowledge required to be president. He responds that it's all about what scale of change we're talking about. He summarizes his political career, starting in 1974. I think grandiose thoughts, he says. This is a grandiose country of people doing big things, and we need leadership to take on big projects.

8:51 p.m.: We're back, and King asks Santorum about Gingrich's remark, before Perry dropped out of the race, that he was the best conservative to go up against Obama and that, therefore, Perry and Santorum should drop out. Santorum responds, Grandiosity has never been a problem with Newt Gingrich. He says Americans don't want a president that will make them worried about what he's going to say next. We can't afford that in a nominee. I'm not the most flamboyant ... but I'm steady, I'm solid.

8:46 p.m.: Commercial break. King teases viewers with the announcement that, as the debate has been going on, Gingrich's campaign has released his tax returns. After the break, we'll find out what's in them.

8:44 p.m.: Applause when Paul mentions his budget plan to cut $1 trillion in the first year. Then he goes into foreign policy, saying that cutting our overseas budget would free up more money for programs at home, and -- unlike in Monday's Myrtle Beach debate, when he got booed -- the audience here in Charleston applauds.

8:43 p.m.: King asks Paul whether he trusts the other three candidates onstage to repeal Obamacare. He says that, whichever Republican is president, it would be possible to repeal, but the likelihood isn't all that good. He says the bigger issue is getting government out of the health care system in general.

8:41 p.m.: Gingrich blasts Santorum's claim that he would have trouble running against Obama on health care. He points out that, as House minority whip in the early 1990s, he led the charge against Hillarycare, and he says he would be happy to engage Obama in a three-hour Lincoln-Douglas-style debate on the issue. I'll let him use a teleprompter. I'll just rely on knowledge, he says.

8:40 p.m.: It doesn't matter whether it's at the federal or state level, Santorum tells Romney: either way, you're defending a plan that is top-down, and that goes against the free market.

8:39 p.m.: Romney responds that his health care plan in Massachusetts did not establish a government-run system, because it did not change anything for the 98 percent of state residents who already had health care before the law passed. He adds that premiums were the highest in the nation before his health care law went into effect, so his law wasn't responsible for that.

8:37 p.m.: Santorum claims that health insurance premiums in Massachusetts under Romneycare are the highest in the nation, and so Romney will have a very hard time running successfully against Obama, because Obama will point out that he based his health care plan on Romney's. He says Gingrich will have a hard time getting elected, too, because he once supported the individual mandate. He then claims that while he was fighting Obamacare, these two guys were playing footsie with the left.

8:35 p.m.: Gingrich says the provision of Obamacare that allows young Americans to stay on their parents' insurance until age 26 wouldn't be necessary to begin with if Obama were pursuing policies to put those young Americans back to work. To parents, he says, Elect us, and your kids will be able to move out because they'll have work!

8:34 p.m.: Gingrich says he understands why the questioner is skeptical: If you've watched Washington and you're not skeptical, you haven't learned anything. But, he adds, it is possible to repeal Obamacare completely -- what voters have to do is elect a president and a Congress committed to doing so.

8:33 p.m.: First audience question: do the candidates really believe that Obamacare can be completely repealed? Romney is up first. He says he will grant states waivers to the best of his ability on his first day in office, and then he will do his very best to shepherd a repeal bill through Congress, which, he says, will hopefully be controlled by Republicans. Then, he says, he would replace it with a bill that would include a similar provision to provide insurance for people with pre-existing conditions, but would treat health care as a market rather than like Amtrak or the Postal Service.

8:30 p.m.: Romney adds that, while it is imperative to balance the budget, we can't do it on the backs of military personnel and veterans. He repeats his new favorite line that the U.S. should have a military so strong no one would think of testing it.

8:29 p.m.: Romney says there should absolutely be incentives for employers to hire returning veterans, but we have to distinguish between federal programs and state programs. The federal government should send the money allocated for veterans' benefits to the states, and the states should be responsible for their own programs for distributing that money.

8:27 p.m.: The same question goes to Santorum, and he says returning veterans should have preference in hiring decisions. We need to be much, much more aggressive about guaranteeing veterans the benefits they need, both economic and medical, he says. He calls the idea of cutting the military budget disgusting.

8:26 p.m.: Paul adds that he gets twice as many donations from active military personnel as the three other candidates combined, and goes on to say that, while economic realities for returning veterans are important, health issues, both mental and physical, are extremely important as well.

8:25 p.m.: King notes that a lot of returning veterans are coming back to a poor economy and few job opportunities. Should the federal government be specifically working on getting jobs for returning veterans, he asks Paul? You really want to make the economy healthy for everybody, Paul says, but helping veterans might be necessary under some circumstances. He references the similar situation after World War II and says the answer wasn't federal work programs, but cutting the federal budget.

8:23 p.m.: Santorum notes that, when talking about capitalism, we shouldn't just talk about high finance or cutting corporate taxes -- we should also talk about capitalism as it applies to ordinary people. He also highlights his proposal to eliminate taxes on manufacturers.

8:22 p.m.: Santorum says, I believe in capitalism that works for the working men and women of this country, who are out there paddling alone in America right now. He accuses Obama of making Americans more dependent on the government through entitlement programs and welfare.

8:21 p.m.: King asks Romney to explain how he reaches the number that Bain created 120,000 jobs. First, he says, I know we're going to get attacked from the left over capitalism. My view is, capitalism works. Free enterprise works. He says that on a stage of Republicans, he shouldn't have to explain how capitalism works. Then he goes through his calculations. Throughout my career I have worked to try to build enterprises, he says. There's nothing wrong with profit, by the way. That profit went to pension funds, to charities, it went to a wide array of institutions. A lot of people benefited from that. And as enterprises become more profitable, they can hire more people. I think Adam Smith was right. ... It is capitalism and freedom that makes America strong.

8:19 p.m.: Gingrich is asked what, specifically, he thinks Romney did wrong as CEO of Bain Capital. He says Bain Capital's business model of buying companies and leveraging them made businesses less likely to survive. Romney is given a chance to respond, but first he turns to Obama's alleged crony capitalism. He also criticizes Obama's recent rejection of the Keystone XL pipeline and calls Obama himself the biggest impediment to job creation in this country.

8:17 p.m.: Gingrich lists three things: repeal the Dodd-Frank bill, which is killing small businesses. We should allow offshore drilling to create well-paying jobs, he says, and overhaul the Corps of Engineers at the local level in South Carolina.

8:15 p.m.: King notes that unemployment is 9.9 percent in South Carolina and asks, should we have specific federal programs to put Americans back to work? Paul says, Most of the things the federal government can do to get us back to work is get out of the way. More specifically, he mentions sound currency and eliminating the income tax.

8:14 p.m.: King asks the other three candidates whether they think Marianne Gingrich's accusations should be an issue in this campaign. Santorum says God is forgiving, but these are issues of character for people to consider. Romney says King should get on to the real issues. Paul says everyone talks about corporations running campaigns, but what about corporations running the media? This debate is starting off on a very antagonistic tone, for sure.

8:11 p.m.: Making his ex-wife an issue so close to the South Carolina primary is as close to despicable as anything I can imagine, Gingrich says. I am frankly astounded that CNN would take trash like that and use it to open a presidential debate. He concludes, The story is false, and finishes off with more anger directed toward the media, accusing them of trying to get Obama re-elected.

8:09 p.m.: The first question goes to Gingrich, about today's accusation by his ex-wife Marianne Gingrich that, when he was having an affair with current wife Callista Bisek, he asked her for an open relationship. He says the negativity of the media has made this country a worse place to live and says to King, I am appalled that you would begin a presidential debate on a topic like that. Standing ovation.

8:07 p.m.: Moderator John King of CNN asks the candidates to introduce themselves briefly. Santorum thanks the voters of Iowa for a little delayed but most welcome victory there. Romney lists his many children and grandchildren. Gingrich says it feels good to be back at home in the South. Paul notes that he is the only veteran onstage tonight.

8:04 p.m.: The candidates just took their places onstage: from left, Rick Santorum, Mitt Romney, Newt Gingrich and Ron Paul. Military cadets are now singing the national anthem, after which the debate will begin.