With three-fourths of the vote counted, McCain, a senator from Arizona, led Mitt Romney, a former Massachusetts governor, by several percentage points and claimed victory.

"Thank you Florida Republicans for bringing a former Florida resident across the finish line first ... in an all-Republican primary," McCain said in Florida.

McCain, who received aviator training in Pensacola, has drawn some support from independents and Democrats in earlier open primaries.

The Arizona senator said his victory "may not have reached landslide proportions but it was sweet nonetheless."

McCain made several references to his time as a POW in Vietnam, saying he thanked his neighbors in "Orange Park for taking such good care of my family" when he was away on a tour of duty "that was longer than expected."

Former New York Mayor Rudy Giuliani was battling it out with former Arkansas Gov. Mike Huckabee for a distant third, with 15 percent and 13 percent respectively. Texas Congressman Ron Paul had 3 percent.

The reports were a disaster for Giuliani, who had skipped the earlier primaries and put most of his eggs in the Florida basket. Early Tuesday, he told NBC News his campaign would continue, no matter what happened in the state.

The Miami Herald said Tuesday's results were a "crushing disappointment" for the Giuliani campaign.

CNN reported Giuliani's campaign was in contact with the McCain camp, saying Giuliani might pull out of the race and swing his support to the Arizona senator.

The candidates were out hunting for votes at the last minute Tuesday. McCain blistered Romney during a St. Petersburg appearance, and Romney returned the favor at a Tampa rally.

McCain benefited from the endorsement of Florida Gov. Charlie Crist and Florida U.S. Sen. Mel Martinez.