TAMPA, Florida - Mitt Romney was poised to retake the lead in the Republican White House race as Florida polls opened on Tuesday after days of brutal campaigning in which he pounded chief rival Newt Gingrich. 

A big win anticipated by polls would propel Romney, a multimillionaire and former Massachusetts governor - back into the lead after a heavy loss to Gingrich in South Carolina that set off an avalanche of negative campaigning. 

The two men have waged an increasingly bitter and personal battle over Florida, the largest state yet to vote in the race to select a candidate to face Democratic President Barack Obama in the November presidential election. 

A relaxed Romney kept his boot on former House speaker Gingrich's neck on Monday, belittling his rival's attacks as "painfully revealing" and, in a sign of growing confidence, canceling a final campaign event set for Tuesday. 

"I tell you, with a turnout like this I'm beginning to believe that we might win tomorrow," Romney told a large crowd in Dunedin on Monday, before training his sights on Gingrich, who has slipped in polls after winning South Carolina. 

"I know the speaker is not real happy, speaker Gingrich, he's not feeling very excited these days," Romney said to cries of mock sympathy from the crowd. 

"I know, it's sad," Romney said. 

"He's been flailing around a bit trying to go after me for one thing or the other, you just watch it and you shake your head. It's been kind of painfully revealing."