ROCK HILL, S.C. (AP) — Attacked as a corporate raider, Mitt Romney defended his record in a new television ad Friday that accuses Republican presidential rivals who criticized his time at the helm of a private equity firm of “embarrassing themselves by taking the Obama line.”

At the same time, Romney’s allies were assailing rival and former Sen. Rick Santorum in ads in South Carolina and Florida for pork-barrel spending as they worked to keep the challenger, who has avoided criticizing Romney’s business past, from catching fire while Romney pushes for a four-state win streak.

“Mitt Romney helped create and ran a company that invested in struggling businesses, grew new ones and rebuilt old ones, creating thousands of jobs,” says Romney’s new ad in South Carolina that lists Staples, Sports Authority and Steel Dynamics as successes of the Bain Capital venture firm. “We expected the Obama administration to put free markets on trial … Romney’s GOP opponents are embarrassing themselves by taking the Obama line.”

That line was a slap at Newt Gingrich and Rick Perry, who have gone after Romney over his Bain tenure and drawn criticism from across the GOP for doing so.

As if on cue, Obama’s campaign released a scathing memo noting that Bain closed companies and cut wages and benefits, while Romney and his partners became wealthy. The memo amounts to a roadmap of the Obama campaign’s general election playbook should Romney become the GOP nominee.

“His overwrought response to questions about it has been to insist that any criticism of his business record is an assault on free enterprise itself,” top Obama campaign aide Stephanie Cutter wrote. “But this is just an attempt to evade legitimate scrutiny of the record on which he says he’s running.”

Romney also rolled out a radio ad about values in South Carolina — likely to counter a TV ad by Gingrich that hits Romney on abortion — and one in Nevada promoting his jobs experience. Romney and his allies are the only presidential campaign entities on the air in Florida, running moderate to heavy levels of ads.

With the Bain issue now spreading across both the primary and general election campaigns, Romney was looking to blunt the force of attacks on the central rationale for his candidacy in hopes of preventing those criticisms from taking hold, if they haven’t already. It’s unclear whether attacks by Gingrich and his allies are having an impact on the race in South Carolina, where unemployment is high.

At a rally at the University of South Carolina at Aiken, Romney was undeterred in stressing his private sector background. He avoided even alluding to the attacks on his Bain record.

“A lot of people want to talk about how we create jobs. By the way, it is not to walk away from free enterprise. It is not to say that there’s something wrong with the free-market system,” Romney told more than 300 people at the event. “No, it’s instead to hold fast to that system and make it work for the American people.”

Gingrich and Perry, each looking to right their struggling bids ahead of the state’s Jan. 21 primary, have described Romney as a greedy corporate raider, not the business-savvy job creator he professes to be.

They’ve been aided by a pro-Gingrich independent group that has pledged to run $3.4 million worth of ads attacking Romney on this issue in South Carolina. So far, less than $1.5 million in airtime has been bought for the ad, which features snippets of people talking about how they lost their jobs when Bain intervened at their companies.

Under pressure from conservatives to scale back the attacks on Romney’s business record, Gingrich released a statement Friday asking the super PAC to edit its advertisements to remove inaccuracies, or pull them.

He also pivoted to accuse Romney of failing as Massachusetts governor to post healthy job gains and argued that that record, too, would be fodder for Obama.

“These are just some of the facts which President Obama would use to undercut Gov. Romney’s claims to be a job creator if he is the Republican nominee,” Gingrich said in the statement.

Santorum, the former Pennsylvania senator, has steered clear of the Bain fight as he aggressively competes in South Carolina, where polls show Romney leading.

Some Republicans think Santorum is well positioned to rise in South Carolina, as he did just before the Iowa caucuses before narrowly losing to Romney. Santorum fared more poorly in New Hampshire but South Carolina is more friendly terrain for the champion of culturally conservative issues.

The Romney-aligned super PAC called Restore Our Future, which is running $2.3 million in TV ads in South Carolina alone, is taking no chances of allowing a more conservative alternative to Romney to emerge and drag the race well into the spring. The group, which spent nearly $3 million on advertising in Iowa attacking Gingrich, was seen as effectively ending Gingrich’s rise in Iowa before the caucuses.

The pro-Romney group is also targeting Santorum on fiscal issues with TV ads and direct mail here and in Florida. Romney is considered the one to beat in Florida, which holds the next primary on Jan. 31.

The commercials assail Santorum’s support for pork-barrel — or earmark — spending while in Congress and his votes to increase the federal debt limit. Both were common positions among Republicans, but have become flashpoints for conservatives angry about spending and the federal budget deficit.

“So how will Santorum beat Obama? Obama knows he can’t,” the ad says.

A flier filling mailboxes in South Carolina makes a similar pitch, stating: “America is in a financial mess because of politicians like Rick Santorum.”

Santorum has stepped up his own advertising and a super PAC supporting him also is airing ads in South Carolina, although so far they have been upbeat messages about the candidate. The group confirmed Friday it was adding an additional $600,000 in advertising time in the state.

Santorum on Friday stepped up his criticism of Romney, calling him “bland and boring” in a fundraising email. He said during a campaign appearance that people would find it hard to vote for Romney because he comes across too much like their boss. Santorum argued that he should be the nominee because he is the best person to challenge Obama.

“We must stop Romney in South Carolina,” he urged supporters in the email. “We must unite and guarantee a conservative standard bearer in 2012.”