The back-and-forth backbiting between Republican presidential rivals Rudy Giuliani and Mitt Romney spilled over into Sunday as Giuliani contended that the former Massachusetts governor has fumbled on health care and economic matters.

Asked by a diner patron about Romney’s health care program while governor, Giuliani said Romney “made a mistake” by mandating coverage for all Massachusetts residents. “When you mandate it, it ends up costing you much more money,” said Giuliani, a former New York mayor.

“He sort of did Hillary’s plan in Massachusetts,” Giuliani said during the second day of a bus tour of New Hampshire.

New York Sen. Hillary Rodham Clinton, the Democratic front-runner for president, pushed for universal health coverage in the mid-1990s when she was first lady.

Romney’s Massachusetts program denies a tax credit, worth about $200, to residents who fail to obtain health insurance, which the state subsidizes for lower-income families. Romney defends the program, saying such incentives nudge more people into getting insurance, which benefits individuals and society in general.

The customer at Suzie’s Diner, who identified himself as a bus driver and former Massachusetts resident, made clear that he did not like Romney’s record and gave Giuliani an opening to take on his rival. Giuliani, who trails Romney in polls in New Hampshire as the Jan. 8 primary approaches, obliged before a crush of news cameras. Romney, he said, “had one of the weaker records of any governor on economics.”

After a campaign event in Newport on Sunday, Romney told The Associated Press: “Let’s compare our records. Mayor Giuliani left a budget deficit of $3 billion — a $3 billion budget gap that Mayor (Michael) Bloomberg called a financial crisis. I left a $2 billion rainy day fund and my last budget left a $500 million surplus.”

Giuliani fielded one hostile question at the diner from Roger Latulippe, a Democrat who said he did not expect to run into a GOP candidate during his breakfast. Latulippe, 67, called for an end to the Iraq war, saying young Americans are dying for an insufficient cause.

“I disagree with you,” Giuliani said calmly. “I think it would be a very big mistake to pull them out while the general there thinks they can still be successful.”

The two candidates had gone at it on Saturday, too. Each tried to characterize the other as a wasteful spender while claiming himself a champion of fiscal restraint.