MANCHESTER, N.H. — Campaign advisers to former Gov. Mitt Romney of Massachusetts, stung by unexpectedly fierce attacks from Republican rivals on his career as a corporate buyout specialist, are scrambling to avoid a prolonged and nasty battle over his business record before it does lasting damage to the front-runner.

Although the advisers had always expected that Democrats would malign Mr. Romney’s work of buying and selling companies, they were largely unprepared for an assault that came so early in the campaign and from within the ranks of their own party, those involved in the campaign discussions said.

Even as Mr. Romney coasted to victory in New Hampshire, they worry that the critique could prove more potent as the race shifts to South Carolina, where shuttered mills dot the landscape, unemployment is higher and suspicion of financial elites is not limited to left-leaning voters.

Some advisers to Romney argue that the most forceful way to rebut the mounting criticism is to prominently tell the stories of winners as well as the losers in the world of private equity: municipal pension funds that invested in his firm, Bain Capital, and rank-and-file workers hired by the companies that Mr. Romney helped turn around.