With Florida's primary looming next Tuesday, the four leading candidates for the Republican presidential nomination clashed in an acrimonious debate Monday night at the University of South Florida in Tampa, bringing up old charges against each other and introducing some new ones as they tried to influence Republican voters in the week they have left.

Riding a wave of momentum after his win in the South Carolina primary on Saturday, former U.S. House Speaker Newt Gingrich is leading in the polls of the Sunshine State, brushing past former Gov. Mitt Romney of Massachusetts who rocketed to the top after his win in the New Hampshire primary.

At the start of the debate, the 18th of the election cycle, Gingrich and Romney took off the gloves, often engaging in personal attacks as moderator Brian Williams of NBC News often focused on them -- with former U.S. Sen. Rick Santorum of Pennsylvania and U.S. Rep. Ron Paul of Texas in the background.

Williams started the debate by asking Gingrich about attacks coming from Romney and his camp, insisting that the former congressional leader was unelectable. Citing Ronald Reagan’s election in 1980, Gingrich brushed off the attacks and pointed to the economic prosperity the country enjoyed during his tenure as speaker in the mid-1990s.

Romney also insisted he was electable and pointed to his leadership record and attacked how Gingrich left Congress.

“He had to resign in disgrace,” Romney said before attacking Gingrich‘s record after leaving office. “He’s been working as an influence peddler in Washington.”

“This is the worst kind of trivial politics,” Gingrich responded, noting that Romney was attacked by his Republican primary opponents during the 2008 election cycle.  

Asked about his attacks after pledging to stay positive, Romney noted that he had learned a lesson after his loss in South Carolina and that he would not be idle when he drew the heat from the other candidates.

Calling himself a “strong conservative," Santorum, who scored a narrow victory over Romney in Iowa, weighed in, noting he had a “path to victory” and attempted to contrast himself with President Barack Obama. Pointing to his record in Pennsylvania, Santorum insisted that he could win Reagan Democrats and beat Obama in the general election. Asked by Williams about his loss in 2006, Santorum noted that Republicans from across the Keystone State went down to defeat that year.

“There’s one thing worse than losing an election and that’s not standing up for the principles you hold,” Santorum said.

Paul jumped in, attacking Gingrich’s record in Congress, though he praised the former congressional leader for taking on the Federal Reserve. Asked about whether he would run as a third-party candidate -- as he did in 1988 -- Paul shot down the idea.

“I have no plans on doing that,” Paul said.

Gingrich responded with praise for Paul’s record on monetary policy and in challenging the Fed.

Asked about his taxes, Romney noted he would release some of his records on Tuesday before turning the topic to public policy, calling for lowering taxes.

“I’ve paid all my taxes that are legally required and not a dollar more,” Romney said. “I’d like to see our tax rate come down and focus on growing the country.”

Gingrich noted that the tradition of presidential candidates releasing their taxes started in 1967 -- with then-Gov. George Romney of Michigan, Mitt’s father. Romney responded that he would release two years of taxes and not the 12 years his father released when he sought the Republican nomination in the 1968 election cycle.

Romney followed it up with a defense of his wealth, insisting he had “helped people around the country” during his years in the private sector.