COLUMBIA, S.C. After enduring days of blistering attacks from his rivals, Republican presidential front-runner Mitt Romney on Thursday defended his record at Bain Capital, a private equity firm that sometimes laid off workers while attempting to turn companies around.

Speaking to reporters after a campaign event in Greer, S.C., Romney responded to comments by former House Speaker Newt Gingrich and Texas Gov. Rick Perry, who have portrayed the former Massachusetts governor as a cold-hearted venture capitalist who put profits ahead of people during his tenure at Bain.

"I think any time a job is lost, it's a tragedy," Romney said.

"There are a number of businesses that we helped start, which collectively, you just look at their websites, added well over 100,000 jobs," Romney said. He named Staples, Bright Horizons Children's Centers, Sports Authority and Steel Dynamics as examples.

"And then the press has also reported on businesses that lost employment, and that was a few thousand jobs that were lost. In each case where there was job loss, there was an effort on the part of the management team to try and preserve the business and to have a brighter future," Romney said, adding: "Sometimes you're successful at that, and sometimes you're not."

Perry presses the issue

Perry continued to press the Bain issue Thursday despite concerns from key Republicans - including South Carolina's Sen. Jim DeMint - that going after a fellow Republican on matters of free-market capitalism was unseemly and could provide President Barack Obama ammunition for the general election.

"It is important for the Republican Party to represent the party that creates jobs, not the party that goes out and identifies companies that they think they can quickly make a buck on and either strip them of their assets and then they go bankrupt or flip them quickly," Perry said in an exclusive interview with The State newspaper of Columbia. "It's a legitimate issue to put out in front of the people. ... We better get this (fleshed) out in January, rather than September," during the general election.

Perry's insistence on attacking Romney for laying off workers at a South Carolina company has cost him the support of a key fundraiser. Barry Wynn, DeMint's treasurer, said Thursday that he was switching his support from Perry to Romney.

"I've spent my whole life, just about, fighting for principles, the main one of which is ... our belief in free-market capitalism," Wynn said. "I just don't think you can be on both sides of that issue."

Perry brushed off Wynn's change of heart, saying, "If somebody wants to cut and run, that's their call." He added that he'll keep criticizing Romney's tenure at Bain.

Gingrich did not bring up Bain in campaign appearances, although a 28-minute TV ad sponsored by a super PAC that supports his campaign continued to run, savaging Romney's tenure at the company. Instead, he extolled the virtues of home ownership and spoke about improving South Carolina's economy at a rally at the statehouse steps in Columbia.

Santorum warns of dependency

Former Pennsylvania Sen. Rick Santorum campaigned on the state's coast, blasting Obama and the dangers of big government.

"Once you become dependent, then the government has you," Santorum told a few hundred people at Sun City Hilton Head. "Ladies and gentlemen, this is an election about whether you're going to leave your children free - period."

Santorum also took some pointed questions from the audience about his conservative credentials because of his votes for the No Child Left Behind education act and the Sarbanes-Oxley Act that tightened financial regulation, votes he now says he regrets.

"I am a consistent conservative," he told the audience. "I didn't say I was perfect."