With just three days before the Florida primaries, Mitt Romney has unleashed a new attack ad against his chief rival, Newt Gingrich.

The ad, which uses a 1997 clip from the day Mr. Gingrich was found guilty by the House of ethics violations, prompted a terse statement from Mr. Brokaw on Saturday in which he expressed concern that his work was being used for political purposes he never intended.

“I am extremely uncomfortable with the extended use of my personal image in this political ad,” he said. “I do not want my role as a journalist compromised for political gain by any campaign.”

NBC’s lawyers have requested that the Romney campaign remove the NBC footage from the ad.

Gingrich, who paid a $300,000 reimbursement fee for the penalty, has emphasized that the ethics inquiry was unfairly partisan. "Whether it was an unprecedented ethics reprimand, his erratic leadership style, or his resignation in disgrace at the hands of his own party, it is understandable why Speaker Gingrich would want to re-write history," Romney spokesman Ryan Williams said in a statement released with the ad.

Romney's campaign said they had received NBC's letter by Saturday afternoon. "We just received the letter; we are reviewing it, but we believe it falls within fair use," senior adviser Eric Fehrnstrom said.