The former New York mayor held no public events a day after squabbling with the former Massachusetts governor over economic issues during a debate in Michigan. Instead, Giuliani dispatched aides and surrogates to accuse Romney of having a "Lawyers Test" for going to war.
Romney retorted that it was Giuliani who had been the lawsuit king as mayor.
A night earlier, Romney said in answering a question on whether he would go to Congress to get authorization to take military action against Iran's nuclear facilities: "You sit down with your attorneys and tell you what you have to do, but obviously the president of the United States has to do what's in the best interest of the United States to protect us against a potential threat."
On Wednesday, Giuliani's campaign derided that response in a statement from Robert Natter, a retired Navy admiral who is a senior military adviser to the candidate.
"Going to war is the most serious decision a president can make," said the statement. "Lawyers should not debate while our national security is on the line. In these momentous decisions, we need leadership, not litigation."
Romney defended himself - and hit back.
"That's a phony issue," he told reporters as he campaigned in Michigan. "I made it very clear. ... I'd make a decision based on the safety of the American people. But of course we'd also check to make sure what our legal and constitutional responsibilities are."
Then, Romney said: "If there's somebody that wants to talk about suing and lawyering, the mayor gets first place."
"The mayor's the one who sued Governor (George) Pataki to keep the commuter tax in place. It's the mayor who sued the government of the United States over the line-item veto. The mayor's the one who shows a propensity to want to put in place a legal test," Romney said, standing on a sidewalk and wearing a blue University of Michigan-Dearborn fleece jacket on a brisk fall day after chatting up customers and supporters at a downtown diner in this city.
"How many times has he sued? He's sued the gun manufacturers, he's sued the president ... he sued on the commuter tax," Romney said as he spent several minutes rattling off a host of lawsuits Giuliani filed during his two terms as New York mayor. He said Giuliani also has sued over immigration and welfare issues.
"The lawyering in history here has to come from the mayor," Romney added.
Responding once more in what turned into a daylong tit-for-tat, Giuliani Communications Director Katie Levinson said, "Hopefully, Mitt Romney isn't going to check with the same group of lawyers who told him the Bill Clinton line-item veto was constitutional."
Little more than three months before voting begins in the GOP caucuses and primaries, both Romney and Giuliani are seeking to stand out and gain the upper hand.
Giuliani leads polls nationally, but Romney has an edge in the leadoff caucus state of Iowa. The race in New Hampshire, another important early voting state, is up for grabs - essentially a toss up between Giuliani, Romney and. Also in the mix in the top tier is , the "Law & Order" actor and former Tennessee senator.
For his part, McCain argued that neither Giuliani nor Romney was innocent of raising taxes.
"They both did," the Arizona senator told radio talk show host Bill Bennett on "Morning In America." "If you want to call them fees or you want to call them bananas, the fact is they're still tax increases when the consumer and the constituent has to pay additional monies into government coffers."
Just before Romney talked with reporters, his campaign sent e-mails to reporters that accused Giuliani of offering "the most muddled and puzzling response of anyone on the debate stage" on the question about whether he would seek approval from Congress to attack Iran.
"It really depends on exigency of the circumstances and how legitimate it is, that it really is an exigent circumstance. It's desirable, it's safer to go to Congress, get approval from Congress," Giuliani said. "If you're really dealing with an exigent circumstance, then the president has to act in the best interests of the country."
Amid the back and forth, Giuliani started running a new radio ad in Iowa touting his fiscal policies. "I lowered taxes," he says in it. "I reduced the growth of government. I made government more accountable, and New York City boomed. A deficit to a surplus. From high unemployment to low unemployment. I have no question that I can do the same thing for Washington that I did for New York City."