SPARTANBURG, S.C. -- Rick Santorum put Newt Gingrich in his crosshairs for the second day in a row, calling the former House speaker "arrogant" for suggesting that he and Rick Perry should drop out of the race in order to let conservative voters coalesce around the Gingrich campaign.

At an event here this morning, the former Pennsylvania senator criticized Gingrich for saying that "it would be helpful" if Perry and Santorum, two rivals for the same slice of the conservative electorate, dropped out.

"The hubris, and I might even go so far as to say the arrogance, of Speaker Gingrich to suggest that I don't have the experience to run a campaign to win a national campaign, having won four elections in four heavily Democratic districts and states, having defeated two incumbent Democrats," Santorum said, using the same two buzzwords -- "hubris" and "arrogance" -- as he did around the state yesterday.

Related: Romney launches offensive in S.C.

Santorum noted that Gingrich's Congressional victories came in a heavily Republican district while Santorum won in areas of Pennsylvania that are traditionally less friendly to Republicans.

Santorum referred to more recent electoral victories on Tuesday, saying that he thought it ironic for Gingrich to be calling for his ouster when Santorum fared better than Gingrich based not only on votes but the amount of time and money spent campaigning in each state.

"New Hampshire... Let me see," Santorum said, facetiously racking his brain in front of reporters after an event in Lexington. "Oh yeah, I finished fourth, ahead of Congressman Gingrich who finished fifth even though he had the New Hampshire Union-Leader endorsement and spent millions of dollars in New Hampshire and I campaigned there for five days and spent twenty thousand dollars."

(Santorum actually finished fifth in New Hampshire with 49 fewer votes than Gingrich).

"So I guess that now that you've lost your first two races to me, that I'm the one that should get out of the race because I won the first two races," he said, referring to Gingrich.

First Thoughts: Newt-mentum returns?

The speaker's comments arose later Tuesday night after a business forum in Columbia, where Santorum talked about them for several minutes while waiting for his car outside the hotel where the forum was held.

"Newt's comments are..." he began, shaking his head. "...out of left field. Ugh. I would never ask someone to get out of the race. I mean, where do you come off telling someone that support me after you beat me twice and support me because I'm the better guy and I can win the race."

Santorum also took a shot at Mitt Romney yesterday after being asked to comment on Romney's revealing that his effective income tax rate is 15 percent.

While he did not overtly claim Romney was paying too little, Santorum did say he thought he was paying more than Romney's percentage.

"I don't know what my effective rate of tax is but I'm fairly confident it's a lot higher than 15 percent," he said. 

SPARTANBURG, SC -- Mitt Romney's campaign launched a barrage of attacks against Newt Gingrich just three days before South Carolina's primary amid signs the former House speaker could threaten Romney's bid for his third straight win in the primary cycle.

The former Massachusetts governor led his campaign in opening a fusillade against Gingrich, who's persisted at or near the top of the polls in tests of Saturday's first-in-the-South primary.

In a sign of how seriously his campaign is taking Gingrich as a threat, Romney broke from his usual form on the campaign trail -- which usually involves attacking only President Obama -- to instead deliver a rebuke of Gingrich's claims on his record on job creation.

"The speaker the other day at the debate was talking about how he created millions of jobs when he was working with the Reagan administration. Well, he'd been in Congress two years when Ronald Reagan came into office, " Romney said. "That'd be like saying 435 congressmen were all responsible for those jobs. Government doesn't create jobs. 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."

Romney's words were just one part of an offensive that extended to his surrogates, who hosted a conference call and launched web videos questioning Gingrich's leadership abilities.

First Thoughts: Newt-mentum returns?

The assault began earlier this morning with a web video released by the Romney campaign entitled "Undisciplined Leader," in which former New York Rep. Susan Molinari, who served with Gingrich in the 1990s, delivered the first blow.

"I served with Newt Gingrich in Congress. Newt Gingrich had a leadership style that can only be described as leadership by chaos,” Molinari said in the video. "I worry about the Republican Party’s chances to defeat President Obama if Newt Gingrich is the nominee."

On a conference call with reporters later in the morning, former Missouri Sen. Jim Talent, another Romney supporter, continued the attack, and warned that if Gingrich were to become the Republican nominee it would hurt the party.

"Each one of us [who served with Gingrich] has personal stories we can tell about going home and having to clean up after our speaker," Talent said. "It had an impact on the 1996 presidential election and, if he's the nominee, it will have an impact on the 2012 election and the impact's not going to be good for the conservative movement and the Republican Party."

If this all sounds familiar, it might be because the Romney campaign employed the exact same tactics following the first surge in the polls Gingrich had enjoyed in Iowa in early December. At that time, Talent and Former New Hampshire Gov. John H. Sununu lanced Gingrich for "off-the-cuff thinking" and "irrational behavior" on a similar conference call, with Sununu continuing to voice the attacks for days in interviews on television and in print.

Related: Santorum targets Gingrich in S.C. stumping

It now appears those attacks may continue. Today, the Romney campaign confirmed reports that Sununu will travel to South Carolina on Thursday to campaign for Romney.

This afternoon, the Gingrich campaign responded to Romney's comments on job creation.

""I fully expect the Romney campaign to be unendingly dirty and dishonest for the next 4 days because they are desperate, they thought they could buy this. They discovered that they can't buy this. I think they have internal polling that shows them loosing. I think they will do anything to try at any level and I need your help. People power will be money power. And I need your help," the candidate said at a town hall meeting.

"If your curious of what kind of leadership style Romney would use as president, today we are seeing what panic looks like," Gingrich spokesman R.C. Hammond told NBC News.

NBC'S Alex Moe contributed to this report.

Pablo Martinez Monsivais / AP

Former House Speaker Newt Gingrich speaks at the Christ Central Community Center in Winnsboro, S.C. on Wednesday.

WINNSBORO, SC -- Newt Gingrich said Wednesday he paid 31 percent of his income in taxes in 2010.

While continuing across the Palmetto State on his bus tour, the former House speaker told reporters he hopes to release his 2012 tax returns tomorrow, which he said he had been told would reflect the fact that he paid nearly a third of his income to the federal government.

Gingrich's statement comes amid efforts by Mitt Romney to parry attacks by his rivals in Saturday's South Carolina primary after Romney had estimated his effective tax burden at about 15 percent over the past year.

It's part of a broader effort by Gingrich and fellow GOP presidential candidate Rick Perry, the governor of Texas, to put pressure on Romney to release his tax returns immediately. The former Massachusetts governor has been reluctant to release his tax records, but has suggested he might make public his most recent returns in April should he have secured the nomination by then.

In the meanwhile, Gingrich has used Romney's words yesterday to needle the frontrunner in the South Carolina primary, a contest which Gingrich has transformed into somewhat of a last stand for conservatives looking to halt Romney's march to the GOP nomination.

“We are going to name our flat tax the Mitt Romney 15 percent flat tax,” Gingrich told the roughly 150-person crowd today. "My goal is not to raise Mitt Romney's taxes, but to let everyone pay Romney's rate."

This back-and-forth between Gingrich and Romney is just one of a number of heated topics between the two campaigns. Gingrich has been especially eager, too, to highlight Romney's private sector record at Bain Capital, the private equity firm he helped found and which led to most of his wealth.

Gingrich seems to be gaining momentum in South Carolina with just three days until the state primary and the Romney campaign is taking the threat to sealing up a sweep of the early nominating states seriously.

In response to the former speaker's push, Team Romney has begun responding, labeling the former Speaker as an “unreliable leader," and holding a press conference call with campaign advisers, creating a new website, and releasing a new web ad.

“I mean where do they get the gall to run these kinds of an ad?” Gingrich told reporters after being informed of the new Romney campaign ad that says he helped re-elect a Democrat. “Maybe they’re bored. Maybe they have excess money. Maybe they want to throw the kitchen sink.”

The speaker is staking his campaign on the primary Jan. 21 and wants conservatives to rally around him as he believes he is the only candidate who can beat Romney.

“I am trying to get every conservative voter in this state to decide, while they may like somebody else, that historically we need to get the vote for Gingrich,” the Speaker said, noting that it would be “helpful” if either Perry or former Pennsylvania Sen. Rick Santorum dropped out of the race.

South Carolina voters will cast their ballots Saturday.

FLORENCE, SC — Speaking to media during an impromptu press conference Tuesday, Texas Gov. Rick Perry twice mentioned rival Rick Santorum's Catholic faith in criticizing his record on fiscal issues.

"Rick Santorum is a good man, he is a good father, he’s a good Catholic," Perry, an evangelical Christian, said. "But he hasn’t always been a good conservative."

The casual but twice-repeated remark — the first time that Perry has publicly pointed to his rival's faith — attracted the attention of journalists because both men are competing to win evangelical voters in the final days before the South Carolina primary.

Perry attends a nondenominational evangelical church and speaks frequently of redemption and his refocus on faith after feeling "lost" in his late 20s.  After the exit of Rep. Michele Bachmann from the GOP presidential campaign, Perry was left remaining as the most vocal evangelical in the GOP field. (Both Santorum and Newt Gingrich are Catholic; Mitt Romney is Mormon. Ron Paul is Baptist but speaks far less frequently about his faith than the Texas governor.)

National reporters who had attended a Gingrich campaign event blocks away from The Drive In restaurant mobbed the governor as he made his way around its tables. Television reporters clambered onto tables and low walls to catch a glimpse of Perry as he chowed down on a gyro burger and onion rings with a state party official.

Despite his religious kinship with a substantial block of Republican primary voters, and his overt courting of socially conservative voters, Perry's campaign has failed to retain his early traction in South Carolina due to the gaffes and misstatements that deflated his frontrunner status.

Asked Tuesday whether he intends to travel on to another primary state after Saturday's vote — a possibility that seems dimmer by the day — Perry joked that he's concentrating on the Palmetto State but could take a victory lap akin to the vacation famously cited by Super Bowl winners.

"We’re headed to South Carolina, South Carolina, and South Carolina," he said. "Then we’ll go to Disney World.”

MURRELLS INLET, SC -- Hoping that his military credentials will offer him a boost in South Carolina's sizable veterans community, Texas Gov. Rick Perry on Tuesday proposed a tax break for returning wounded soldiers "to help to get their lives back."

At a VFW hall outside of Myrtle Beach, the Texas governor suggested that "post 9/11" veterans certified as wounded by the Department of Defense should receive a five year exemption from paying a personal income tax. 

"If you sacrificed that much for your country, the least this country can do is give you that type of support when you come back," he told about 50 audience members in the hall. 

Perry, the son of World War II tailgunner and himself an Air Force veteran, is the only candidate in the field other than former flight surgeon Ron Paul to have served in the military. He was accompanied Tuesday by South Carolina native and Medal of Honor recipient Lt. Mike Thornton.

As the governor of Texas in 2009, Perry signed into law a full property tax exemption for veterans who are classified as 100 percent disabled. 

In remarks that contained no specific critiques of his opponents, Perry said that the tax break would be an enduring message about the value of military sacrifice. 

"That’s sending the message. That’s sending the message that will last longer than a parade, that will last longer than a proclamation on the war, than a pat on the back," he said. 

After his remarks, Perry spoke at length with attendees, telling one questioner that he would seek to eliminate the Small Business Administration. 

"I''d just do away with them," he told a man who complained that the SBA was "all talk." 

President Barack Obama proposed last week to consolidate the SBA, the Commerce Department, and numerous other trade and business agencies. He also elevated the head of the SBA to a cabinet-level position. 

Updated 1:35 p.m.

FLORENCE, S.C. -- Mitt Romney estimated Tuesday that he pays about a 15 percent effective tax rate on his earnings, a much lower rate than many middle-class Americans pay.

Facing increasing pressure from his GOP rivals, particularly former House Speaker Newt Gingrich and Texas Gov. Rick Perry, to release his tax records, Romney seemed to commit to release some returns after having been somewhat cagey on the topic at last night's presidential debate.

If and when those records are released, Romney suggested they would show he pays about 15 percent of his earnings to the government.

"It’s probably closer to the 15 percent rate than anything,” Romney said in response to a question about his effective tax rate. “Because my last 10 years, I’ve — my income comes overwhelmingly from investments made in the past, rather  than ordinary income, or rather than earned annual income.”

Romney's tax rate has been subject to much speculation since the multi-millionaire former CEO told reporters months ago that he would comply with all financial disclosure laws, but had no intention of releasing his tax returns as has been traditional among presidential nominees since the 1970s.

Since December, much of the fire directed toward Romney on this issue had come from Democrats, but last week, Gingrich said he would release his returns this Thursday, and called on Romney to do the same. At last night's debate in Myrtle Beach, Perry also tweaked Romney, saying he should release his tax returns publicly, before the nomination process concluded.

"Mitt, we need for you to release your income tax so the people of this country can see how you made your money. And I think that’s a fair thing. Listen, here’s the real issue for us, as Republicans, we cannot fire our nominee in September," Perry said last night. "We need to know now. So I hope you’ll put your tax records out there this week so the people of South Carolina can take a look and decide if, you know, we’ve got a flawed candidate or not."

Romney hedged last night on whether he'd release those records, but appeared to be more definitive on Tuesday.

"We looked at prior races for president, and in prior races for president the tradition has been that the nominee releases his tax returns in tax season, in April," Romney said. "And I know that if I'm the nominee, people will want to see the most recent year, and see what happened in the most recent year and what things are up to date and so they'll want to see the tax returns that come out in April, so rather than sort of have multiple releases of tax returns, why-- we'll wait until the tax returns for the most recent year are completed, then release them."

The tax issue is an especially sensitive issue for the Romney campaign, given the former Massachusetts governor's status as the wealthiest of the presidential candidates. He is estimated to be worth around $200 million, according to financial disclosure documents. Much of that wealth came as a result of Romney's work for Bain Capital, the private equity firm he had cofounded.

Federal tax rates vary from 10-35 percent of income for most Americans, with state and municipal taxes adding to the burden. Given Romney's wealth, he would be in the highest bracket, if he were taxed on earned income. 

But Romney pays a much lower rate because most of his income comes from investments, which are taxed at lower rates. Warren Buffett, who also derives much of his income from investments, has said this is unfair.

The tax burden someone like Romney would face cuts to the core of the fiscal debate that has roiled Washington over the past year. President Obama has called on the wealthy to shoulder a larger share of the tax burden, especially since they benefit from a more favorable tax rate on earnings gleaned from nontraditional sources of income, like investments, dividends or interest.

Romney addressed that argument to an extent, noting his opposition to Gingrich's proposal to eliminate all capital gains taxes.

"You’d have individuals – the Warren Buffett argument -- Warren Buffett, Bill Gates would probably pay no taxes at all," he said. "Today they probably pay 15 percent. Very high-income people of this country pay roughly 15 percent of taxes if their resources are coming from investments and under their plan it would go to zero. I just don’t think that’s the right course."

Romney provided no indication as to what level of taxes he thought the wealthy should pay on their investment-related income, but said he thought savings in the tax code should be directed toward providing tax relief for the middle class, and lowering corporate income taxes.

MYRTLE BEACH, SC-- Making a rare debate-day appearance at a revival meeting-like event packed with Christian conservative voters, Mitt Romney tweaked his traditional stump speech to highlight a handful of social issues he rarely mentions unprompted on the trail.

Romney's appearance -- along with those of the other four remaining presidential candidates -- at today's Faith and Freedom Coalition event underscores the importance of the conservative Christian vote here. In a December NBC News/Marist poll of likely South Carolina voters, 44 percent identified themselves as fundamentalist or evangelical Christians, and capturing even a slice of this constituency could help Romney close out his third consecutive primary victory in a state where most polling shows him holding onto a narrow lead.

The former Massachusetts governor's brief remarks today went beyond his normal jobs-and-economy-focused message to contrast his positions on social issues with those of President Obama.

"[Obama's] path is one which sends the vice president of the United States to China, where he tells the people there that he understands their one child policy -- where he understands ... all that's associated with it, the abuses associated with that policy." Romney said. "My view is the next president  of the United States should stand up for the sanctity of human life in the United States, and anywhere in the world in which it is threatened."

"This president has tried to pave the path for same-sex marriage to spread across the country," Romney continued. "My view is that we should defend the defense of marriage act and that we should have a constitutional amendment that defines marriage as a relationship between a man and a woman."

Romney also made mention of new endorsers Jay and Jordan Sekulow, heads of the conservative American Center for Law and Justice, with the elder Sekulow well known for arguing conservative social causes before the Supreme Court.

Not mentioned by Romney this afternoon: his's newest endorser, former presidential candidate Jon Huntsman, who suspended his campaign and endorsed Romney at a press conference this morning.

"Now I know why we had a hard time confirming Jon Huntsman," Faith and Freedom coalition chairman Ralph Reed joked near the end of the event. "I was in touch with his campaign all day yesterday."

COLUMBIA, S.C. – After Rick Perry's attacks on Mitt Romney's private-sector resume cost him one high-profile South Carolina supporter Thursday, another influential Perry backer said he won’t change his endorsement but also asked for the Bain Capital jabs to stop.

David Wilkins, a former U.S. ambassador to Canada who endorsed Perry in August, told NBC News that he had voiced his dislike of Perry’s anti-Bain attacks with the campaign here.

"I think it's sort of ironic for Republicans to be attacking each other on capitalism and the free-enterprise system, which is something our whole party is based on," Wilkins said.

Earlier Thursday, Barry Wynn, a financial adviser and former chairman of the South Carolina Republican Party, told the Washington Postthat Perry's criticism of Romney's Bain record "kind of moved me over the top," compelling him to switch to the Romney camp.

Wilkins, a former South Carolina speaker of the House, said Perry and his Republican rivals "ought to accentuate the positive in everybody's campaign and leave the negatives to the other side and not be cutting each other up so much."

Wilkins was more supportive of Perry's TV ads, which tout his military record and Christian conservatism, calling them "extremely positive" and "professionally good."

Related story: Perry backs off 'vulture' attack on Romney and Bain

BLUFFTON, SC -- Rick Santorum told South Carolinians this morning that they have a duty to their country, not to put on a uniform, but to choose a Republican presidential nominee that will provide a "stark contrast" to President Obama.

"We cannot afford to have our nominee as the issue in this race," Santorum told an auditorium crowded with more than 200 members of a retirement community.

The jab came after Santorum pointed to the health care legislation Mitt Romney signed as governor of Massachusetts and his support of the economic bailout. The former Pennsylvania senator said the same attacks that Republican presidential candidates are using against Romney are the ones Democrats will employ if he is the nominee.

Class warfare and the role of government have been themes for Santorum since arriving in South Carolina. He has hit both the president and GOP candidates Newt Gingrich and Rick Perry for rhetoric he says attacks Americans for being successful.

In addition to attack capitalism, Santorum accused the president of trying to expand government to create dependency. Santorum said reliance on entitlement programs "hooks people like a narcotic. It makes you less than you can be."

He'll make four more stops in the Palmetto State today.