A win by Romney would again reset the 2012 GOP race, seen early this month as his to lose, then thrown into doubt by Gingrich's come-from-behind win in South Carolina.
Romney easily won the New Hampshire primary after nearly winning the in leadoff Iowa. The South Carolina setback behind him, Romney sought to aggressively stop Gingrich, aided by a well-funded political action committee that supports him and is run by former political aides.
Together, Romney's campaign and the supportive group Restore Our Future have combined to spend $6.8 million on television ads in the final week of the Florida campaign, about three times what Gingrich and a group supporting him have spent.
Romney capped his Iowa, New Hampshire and South Carolina campaigns with upbeat spots. Nothing doing in Florida, where he was running out the clock with ads attacking Gingrich over Freddie Mac and an ethics violation in Congress.
But Romney dropped any reference to Gingrich at his final stop Monday at The Villages in central Florida. And instead of reciting the lyrics of "America the Beautiful," as he typically does, Romney — on pitch — broke into song and led the crowd in a reverent rendition.
Rick Tyler, a former top Gingrich aide now running a pro-Gingrich political action committee, showed up at Romney's kickoff event in Jacksonville on Monday, stealing a page from Romney's Florida playbook.
"I'm here to get as many cameras and microphones so I can talk about Mitt Romney's incessant failure to tell the truth," Tyler said.
Gingrich said he was confident he could narrow Romney's margin in public voter surveys, even as he and his campaign began trying to soften the blow a defeat in Florida might bring.
Gingrich aides tried to diminish the state's impact on the quest for the nomination by issuing a memo from his political director, Martin Baker.
It noted that by Wednesday morning, only 5 percent of the 2,288 national convention delegates will have been awarded.
Gingrich, who has promised to campaign through the national convention this summer, was clearly looking to regroup after Florida.
"The campaign is shifting to a new phase where opportunities are not limited to a single state," Baker wrote.
Gingrich had not announced his plans for Wednesday. Romney, who has already begun advertising in next-up Nevada ahead of the state's Feb. 4 caucuses, was traveling there Wednesday, and to Minnesota, which holds its caucuses on Feb. 7.
Associated Press writers Kasie Hunt in The Villages, Shannon McCaffrey in Tampa and Brendan Farrington in Miami contributed to this report.