In a state where more than one in five residents is on Social Security, Romney hit Perry hardest on the issue of preserving the federally run retirement savings program. "I think by the measure of the tens of millions of people that rely on Social Security, it's a success," Romney said at a Town Hall-style meeting that attracted about 70 people. "Ronald Reagan believed in Social Security. I believe in Social Security."

His comments, in advance of Saturday's straw poll held by Florida Republicans, elicited a response from Perry, also stumping in Florida.

"Every person who is on Social Security and any individual who has planned their retirement with that, they need to know one thing: America has promised that that program will be there," Perry said after a private fundraiser in Fort Lauderdale. "And for anyone to say differently, particularly someone standing on the Republican stage who wants to be the nominee for the presidency, to imply that the age-old Democrat trick that we're going to go scare our seniors - that's pretty irresponsible."