Mitt Romney is defending himself against attacks that he was once more of a corporate raider than a job creator.

A new television ad airing in South Carolina today accuses Romney's rivals for the Republican presidential nomination of "embarrassing themselves by taking the Obama line." Newt Gingrich and Rick Perry have gone after Romney over his time at Bain Capital, saying the venture firm's acquisitions generated profits at the expense of layoffs.

President Barack Obama's campaign added to the criticism, noting that Bain closed companies and cut wages and benefits, while Romney and his partners became wealthy.

But Romney's ad says Bain "invested in struggling businesses, grew new ones and rebuilt old ones, creating thousands of jobs." It lists Staples and Sports Authority among the company's successes.

Meanwhile, Romney allies are also going after Rick Santorum, who has been gaining more attention since finishing just eight votes behind Romney in Iowa. Ads accuse Santorum of pork-barrel pending while representing Pennsylvania in the U.S. Senate.

Santorum has stayed out of fight over Romney's business record, but today criticized the former Massachusetts governor, saying he's too much like people's bosses.