The two leading candidates for the U.S. Republican Party's presidential nomination traded sharp attacks during a nationally televised debate in Florida Monday, days before that state's crucial primary election.

Former Massachusetts Governor Mitt Romney went on the offensive against rival Newt Gingrich, prompted by Gingrich's upset victory in last week's South Carolina primary. Romney accused Gingrich of being an “influence peddler” for his work as a consultant with Freddie Mac, the government-backed mortgage giant blamed by many for contributing to the U.S. housing crisis.

Romney also attacked Gingrich's ethics, accusing him of resigning in disgrace as speaker of the House of Representatives in the 1990s.

For his part, Gingrich accused Romney of spreading falsehoods about his record, and recalled statements by Romney's 2008 presidential opponents who said the former governor “can't tell the truth.”

Gingrich heads into the January 31 primary with the momentum after last week's win over Romney and two other Republican rivals, former senator Rick Santorum of Pennsylvania and Texas Congressman Ron Paul in South Carolina.

The four candidates were also asked about President Barack Obama's dealings with Iran. Romney said Tehran's threats to block the Strait of Hormuz and choke off global oil supplies amount to an act of war, while Gingrich and Santorum said Mr. Obama's Iran policy was a failure. Paul said there is no justification for the U.S. to use military force against Iran.

So far, there have been three different winners in the three Republican nominating contests: Santorum won the Iowa caucus, Romney won the New Hampshire primary, and Gingrich in South Carolina. The eventual nominee will face Mr. Obama, the Democratic incumbent, in the November general election.