That said, neither Mr. Romney nor Mr. Perry seemed to need much prompting.

Mr. Romney argued that Mr. Perry, who has spent much of his life in government, lacked the experience in private industry needed to turn the economy around. And seeking to undercut what has been Mr. Perry’s main claim in advancing his candidacy — his record as governor — Mr. Romney argued that Mr. Perry had benefited from institutional advantages, ranging from a Republican state legislature and state Supreme Court to the economic benefits of having vast deposits of gas and oil.

“Those are wonderful things, but Governor Perry doesn’t believe that he created those things,” Mr. Romney said. “If he tried to say that, well, it would be like Al Gore saying he invented the Internet.”

The exchanges quickly moved from the economy to health care. The candidates were asked to register their opinions on the health care plan that Mr. Romney signed into law in Massachusetts.

Mr. Perry chimed in first, declaring, “It was a great opportunity for us as a people to see what will not work, and that is an individual mandate in this country.”

Mr. Romney sought to defend the health care law, which was a precursor to the federal plan signed into law by Mr. Obama, but said it was intended for his state only. If elected, he said, he will move to repeal the Obama administration’s law as soon as he takes office.