Romney is now calling on Judge Kathe Tuttman to resign. This summer, Tuttman freed Daniel Tavares, who had served 16 years for killing his mother, and did not require him to wear a monitoring bracelet. Tavares now stands accused of killing a young married couple in Washington state last week.
"I think that the judge showed an inexplicable lack of good judgment," said Romney.
Rudy Giuliani, whose crackdown on crime while mayor of New York City is a centerpiece of his campaign, began the attack on Romney.
"This whole appointment of a judge goes to a much bigger point -- that Governor Romney had a very poor record in dealing with murder and violent crime as governor," said Giuliani.
Giuliani pointed to FBI statistics showing murders and robberies rising in Massachusetts during Romney's term. Romney's campaign countered that overall crime, including car thefts and larcenies, dropped 8 percent during his four years in office. And the candidate himself fired back...hard.
"Of all the people who might attack someone on the basis of an appointment, I thought he would be the last to do so," said Romney.
Romney was referring to one of Giuliani's police commissioners, Bernard Kerik, who's now under federal indictment.
"He put someone in place as commissioner who had a very questionable past, and then recommended to the president of the United States this person be made the secretary of Homeland Security," said Romney.
The spat comes as Giuliani, the national front-runner, tries to gain greater traction in New Hampshire, where he trails Romney.
Meanwhile, former Tennessee Senator Fred Thompson is going after Giuliani for his position on guns.
"He simply supported just about every gun control legislation that came down the pike," said Thompson. "And I just disagree with him on that. I saw he was at bill-signing ceremonies with Chuck Schumer and President Clinton and others for gun control legislation over the years, and he was very outspoken about it. Of course, he's not as outspoken about it anymore."
Thompson is also attacking Romney for his change of heart over the years on abortion rights, which Romney now opposes.
"Until about two years ago, when he decided to run for president, Governor Romney was the most adamant pro-choice advocate that I've ever seen," said Thompson recently.
Roger Simon, chief political columnist for Politico.com, tried to put the Republican political attacks in context.
"Rudy Giuliani is trying to slow Mitt Romney down," said Simon. "Rudy Giuliani cannot afford to have Mitt Romney win all the early states. We're in the end game now. If you've got something to use against an opponent, you better use it now."