MIAMI - Sen. John McCain won a breakthrough triumph in the Florida primary Tuesday night, gaining the upper hand in the battle for the Republican presidential nomination ahead of next week's contests across 21 states and lining up a quick endorsement from soon-to-be dropout Rudy Giuliani.
"It shows one thing. I'm the conservative leader who can unite the party," McCain said after easing past former Massachusetts Gov, Mitt Romney in a hard-fought contest.
"It's a very significant boost, but I think we've got a tough week ahead and a lot of states to come," he said in an interview with The Associated Press.
Sen. Hillary Rodham Clinton was the Democratic winner in a primary held in defiance of national rules that drew no campaigning and awarded no delegates.
The victory was worth 57 national convention delegates for McCain, a winner-take-all haul that catapulted him ahead of Romney for the overall delegate lead.
Giuliani ran third, his best showing of the campaign but not nearly good enough for the one-time front-runner who decided to make his last stand in a state that is home to tens of thousands of transplanted New Yorkers.
In remarks to supporters in Orlando, the former New York mayor referred to his candidacy repeatedly in the past tense - as though it were over.
"We'll stay involved and together we'll make sure that we'll do everything we can to hand our nation off to the next generation better than it was before," Giuliani said.
Former Arkansas Gov. Mike Huckabee trailed, but told supporters he would campaign on. Texas Rep. Ron Paul was fifth, and last.
Romney, who has spent millions of dollars of his personal fortune to run for the White House, also vowed to stay in the race.
"At a time like this, America needs a president in the White House who has actually had a job in the real economy," he told supporters in St. Petersburg.
Florida marked the end of one phase of the campaign, the last in a series of single-state contests.
The campaign goes national next week, with 21 states holding primaries and caucuses on Tuesday and 1,023 party convention delegates at stake.
Returns from 73 percent of the state's precincts showed McCain, the Arizona senator, with 36 percent of the vote and Romney, the former governor of Massachusetts, with 31 percent.
The victory was another step in one of the most remarkable political comebacks of recent times. McCain entered the race the front-runner, then found his campaign unraveling last summer as his stands in favor of the Iraq War and a controversial immigration bill proved unpopular.
The war gradually became less of a concern after President Bush's decision to increase troop deployments began to produce results. McCain also sought to readjust his position on immigration.
By the time of the New Hampshire primary, he was primed for victory, and got it. He won the South Carolina primary last week, taking first place in the state that had snuffed out his presidential hopes in 2000.
McCain's victory was his first-ever primary win in a state that allowed only Republicans to vote. His previous triumphs, in New Hampshire and South Carolina this year, and in two states in 2000 came in elections open to independents. He campaigned with the support of the state's two top Republican elected officials, Gov. Charlie Crist and Sen. Mel Martinez.
Romney's only primary win so far was in Michigan, a state where he grew up and claimed a home-field advantage. He also has caucus victories to his credit in Wyoming and Nevada.
A survey of voters as they left their polling places showed the economy was the top issue for nearly half the Republican electorate.
McCain led his rival among those voters, blunting Romney's weeklong effort to persuade Floridians that his background as a businessman made him best-suited for heading off a recession.
McCain also benefited from the support of self-described moderates, as well as older voters and Hispanics. Giuliani ran second among Latino voters, according to preliminary exit poll data.
Romney was favored by voters opposed to abortion and to easing the path to citizenship for illegal immigrants.
About 40 percent of self-described conservatives supported him, as well, compared to about 25 percent for McCain.
The poll was conducted by Edison Media Research and Mitofsky International for The Associated Press and the television networks.