Washington (CNN) -- With a healthy lead in final polls the day before the Florida primary, Mitt Romney depicted chief rival Newt Gingrich on Monday as increasingly desperate in the race for the Republican presidential nomination.
Romney and Gingrich continued to clash over the negative turn in the campaign between the two front-runners, with Gingrich accusing Romney of dishonesty.
"He has been flailing around a bit trying to go after me for one thing or the other," Romney told supporters in a last-day stop in Dunedin, outside St. Petersburg. "You just watch it and shake your head. It has been kind of painfully revealing to watch."
After losing to the former House speaker in the South Carolina primary, Romney and his allies have pounded his leading rival over Florida's airwaves -- a strategy that helped flatten a Gingrich surge before the Iowa caucuses. Late polling shows Romney leading by a double-digit margin in Florida, and Gingrich conceded Tuesday that the wave of attack ads by the former Massachusetts governor has been effective.
But Gingrich told supporters in Orlando that he would keep fighting beyond Tuesday's contest and would be back for the GOP convention in Tampa.
"We are going to tell the truth," Gingrich said. "We're going to beat a big lie campaign with a truth campaign. We're going to beat money power with people power. And we are going to go all the way to the convention, and we are going to win in Tampa, and we are going to the nominee, with your help, of the Republican Party."
Gingrich spent last week refuting ads that highlight ethics violations he faced during his 1995-1998 tenure as House speaker, link him to the housing crisis as a Washington insider consulting for Freddie Mac and question his ties to conservative icon Ronald Reagan. Romney and his allies are outspending Gingrich and his supporters 4-to-1, mostly to attack Gingrich.
"I'll tell you what, there's nothing like 17-and-a-half million dollars in false ads to make a big difference," Gingrich told CNN. "The reason I seemed flat in the second debate in Florida is I have never seen a candidate for president that methodically dishonest."
Earlier, Romney told NBC's "Today" show that his campaign was forced to respond to negative ads by Gingrich in South Carolina.
"We were being whaled on by Speaker Gingrich and didn't respond well in South Carolina," Romney said. "So we decided to respond. We made it clear if people want change in Washington you have to bring in someone from outside Washington. Both the change in tactic as well as the message have had a real impact in Florida."
But Gingrich's campaign argues that even after Florida's 50 convention delegates get claimed in the winner-take-all primary, neither candidate will have more than 10% of the 1,144 delegates needed to win the GOP nomination at the August convention in Tampa.
Martin Baker, the Gingrich campaign's national political director, said Monday that with most future primaries and campaigns awarding delegates on a proportional basis, rather than the winner-take-all approach in Florida, Gingrich will build his delegate count in coming months.
"Mitt Romney has failed to consolidate conservatives in each of the first four contests with every notable grass-roots conservative endorsement -- Herman Cain, Fred Thompson, Michael Reagan, Rick Perry and others -- going to Newt Gingrich," Baker said.
The Florida primary is open only to the state's 4.1 million registered Republicans. So far, state officials say more than 630,000 people have cast absentee ballots or voted early -- a figure that tops all votes cast in South Carolina.
Romney finished a close second to former Pennsylvania Sen. Rick Santorum in the Iowa caucuses, then easily won the New Hampshire primary before Gingrich's strong victory in South Carolina. Baker said what he called the Romney campaign's "false and negative attacks" and its huge funding advantage had affected the more than 200,000 absentee ballots cast in Florida before Gingrich's South Carolina victory.
"The bottom line: Regardless of the message the Romney campaign wants to push and the media wants to deliver, this race is just getting started," Baker said.
And a leading Gingrich backer in Florida, former Attorney General Bill McCollum, said Monday that Santorum should drop out because he had no chance of eclipsing Gingrich as the main conservative in the GOP race.
"If he weren't in it, we would clearly be beating Romney right now," McCollum told CNN in reference to Santorum, later adding: "I don't know how long he stays in it. He is a friend. I know him well. But I think a vote for Rick is simply not a vote -- I think it is a vote that is wasted at this point."
Both Santorum and Paul have conceded Florida because the winner-take-all format gave them no realistic chance to secure delegates. Paul spent the weekend campaigning in Maine for caucuses that run through February 11, while Santorum canceled his Sunday events in Florida to be with his hospitalized daughter, Bella, in Pennsylvania.
Santorum told CNN's "John King USA" that while the 3-year-old "had a very tough Friday and Saturday," she has recovered to the point where he can return to the campaign trail. But rather than return to Florida, he changed his schedule and headed for Missouri to begin a swing through several states holding upcoming caucuses and primaries.
"We're just showing this is a national campaign," Santorum said. "We have resources deployed here. We're going to be spending money in all these states, and we're hiring staff and have, in fact, hired staff in some of the other states coming up on Super Tuesday. This is a race that we believe will come to us at some point, and we'll be able to take advantage of it when it does."
CNN's Joe Johns, Kevin Liptak, Shawna Shepherd, Adam Aigner-Treworgy and Paul Steinhauser contributed to this report.