MANCHESTER, N.H. — Surging in New Hampshire, John McCain seemingly should be the candidate taking heat from his Republican presidential opponents. But Mitt Romney was the one assailed during and after a high-stakes GOP debate.

Romney's rivals want to cripple his campaign with searing losses in Iowa and New Hampshire that would hamper the wealthy former Massachusetts governor in states beyond. They also don't particularly care for him.

Back and forth it went on Sunday, two days before the primary and only hours after Saturday night's debate.

"My friend, you can spend your whole fortune on these attack ads, but it still won't be true," McCain told his chief competitor Saturday night, taking issue with Romney's characterization of the Arizona senator's immigration plan as amnesty.

"I don't describe your plan as amnesty in my ad, I don't call it amnesty," Romney shot back — even though two of his TV commercials use the term, including on that says McCain "wrote the amnesty bill that America rejected."

On Sunday, Romney acknowledged: "I was incorrect."

The immigration skirmish was just one of several in which Romney was on the defensive. A candidate forum at 8 p.m. EST Sunday could bring more of the same.

"The guy with the ball is the guy people are trying to tackle," Romney told ABC News' "This Week" on Sunday morning, brushing aside the criticism of the night before. Pressed about the frequent characterization of him as a flip-flopper, Romney blamed his chief rival in New Hampshire, saying: "The McCain campaign from the very beginning did a masterful political job of trying to tag me with that."

Romney argued that his positions as he runs for president are consistent with the actions he took as governor — despite evidence that he has shifted to the right on some issues. He castigated politicians who he said are more interested in personal insults than changing government — even as his campaign sought to portray McCain as a nasty candidate who has a record of personally attacking his opponents.

McCain, for his part, tried to walk a careful line.

"He has changed his position on almost every major issue," McCain said of Romney on NBC's "Meet the Press" on Sunday. He added: "That doesn't mean he's not a good person."

Mike Huckabee acknowledged "a brotherhood" of sorts with McCain, fueled by Romney's criticism. "We have both been brutally assaulted by Governor Romney with amazingly misleading ads that attacked and distorted and misrepresented our records, Romney attacking me in Iowa, attacking him in New Hampshire," Huckabee said on "Fox News Sunday."