I think it might have been someone whispering that to *Russert*, to remind him to mention that Reagan raised taxes in his question. Here's the transcript:http://www.cfr.org/publication/15325/
MR. RUSSERT: Governor Romney, you are a big fan of Ronald Reagan. Will you do for Social Security what Ronald Reagan did in 1983?
MR. ROMNEY: I'm not going to raise taxes. What I'm going to do --
MR. RUSSERT: Well, Ronald Reagan raised the payroll tax, and he also raised the retirement age, and he saved Social Security with Alan Greenspan and Tip O'Neill and Bob Dole and Pat Moynihan.
Notice how in the initial question, Russert just asks "will you do what Reagan did with Social Security...." without mentioning what that was. He was probably supposed to include that mention of what exactly Reagan did in his question, so someone whispered that to him as Romney was starting to answer the question, and he interrupts Romney to complete the question.