Republican Rudy Giuliani and Democrat John Edwards were dropping out of the US presidential race Wednesday, narrowing down wide-open White House races for both parties to two top candidates. John McCain emerged as the clear front-runner for the Republican presidential nomination with a victory over former Massachussetts governor Mitt Romney in the hotly contested Florida primary on Tuesday. The veteran Arizona senator lined up a quick endorsement from Giuliani before national contests on Feb. 5, a series of 21 contests that could cement the White House nomination for the Republicans. "John McCain is the most qualified candidate to be the next commander in chief of the United States," Giuliani said. "He's an American hero." Once the front-runner himself, Giuliani decided to abandon the race after a dismal performance in Tuesday's Florida primary, a contest on which he had bet his political fortune. Instead, McCain won and Giuliani came in a distant third. Tuesday's result was a remarkable collapse for Giuliani. Last year, he occupied the top of national polls and seemed destined to turn conventional wisdom on end by running as a moderate Republican who supported abortion rights, gay rights and gun control. The results seriously decimated Giuliani's unconventional strategy, which relied heavily on Florida to launch him into the coast-to-coast February 5 nominating contests. Edwards' withdrawal turns the heated Democratic contest into a battle between Barack Obama and Hillary Rodham Clinton, who won a largely symbolic victory in Florida. No Democratic delegates were at stake and no candidates campaigned there because of a dispute between the state and national parties over the date of the primary. Speaking to a crowd in New Orleans on Wednesday, Edwards said it was time to "step aside "so that history can blaze its path" in the race between a black man and a woman for the White House. "With our convictions and a little backbone we will take back the White House in November" from the Republicans, he said. The former North Carolina senator had lost the previous four state contests, unable to overcome the star power of Obama and Clinton. The impact of Edwards' decision will be felt in one week's time, when Democrats hold primaries and caucuses across 22 states, with 1,681 delegates at stake. Four in 10 Edwards supporters said their second choice in the race is Clinton, while a quarter prefer Obama, according to an Associated Press-Yahoo poll conducted late this month. An immediate impact of Edwards' withdrawal will be the addition of six of Edwards' delegates for Obama, giving him a total of 187, and four more for Clinton, giving her 253. A total of 2,025 delegates are needed to secure the Democratic nomination. McCain's victory in Florida was worth 57 Republican National Convention delegates, a winner-take-all haul that catapulted him ahead of Romney for the overall delegate lead. More than 1,000 Republican delegates will be awarded on Feb. 5 in 21 primaries and caucuses. A total of 1,191 delegates are needed to secure the nomination at this summer's Republican national convention. McCain, a former Vietnam prisoner-of-war, had been the early front-runner in the race only to see his campaign largely collapse last year. He rebounded with a coveted New Hampshire primary win on the back of support from independents. Still, many of the party's core conservative base remain wary of him, considering him too much of a maverick. But with his victory in Florida, there were signs McCain may be breaking through as the choice of the party establishment and a candidate able to unite all wings of the Republican Party. If so, he may be unstoppable. Giuliani's exit could help McCain in more moderate delegate-rich states slated to vote next week, like California, New York and Illinois. But it also could give Romney fodder to claim that McCain is not the truest conservative in the race, because Giuliani is seen as liberal on social issues. A disappointed Romney promised to press on after his second place finish following a tough Florida battle in which he traded insults and accusations with McCain. He said Wednesday that McCain may not be conservative enough to win the nomination. "I think what will happen across the country is that conservatives will give a good thought to whether or not they want to hand the party's nomination over to Senator McCain," Romney said on ABC's "Good Morning America." Among the others, Mike Huckabee, the former Arkansas governor and Baptist preacher who won Iowa, remains in the race, but has little money and finished a distant fourth in Florida. He could however split the conservative vote with his strong support among the religious right, a possible boost for McCain. Texas Rep. Ron Paul has made no move to withdraw even though he scores in single digits in voting. Clinton, locked in a tight race with Obama, looked at her wide margin of victory in Florida to boost her campaign ahead of "Super Tuesday". Both candidates have toned down harsh rhetoric ahead of those contests, in which 1,600 delegates are at stake. A total of 2,025 delegates are needed to secure the Democratic nomination at the party's convention in August. Campaigning in Denver, Obama elevated McCain as the likely Republican nominee and depicted Clinton as a calculating, poll-tested divisive figure who will inspire greater partisan divisions as she sides with Republicans on issues like trade, the role of lobbyists in politics and national security. He depicted himself as the clear contrast to the rival party. At a campaign stop in Arkansas, where her husband, former President Bill Clinton, was governor, Clinton proposed more protections for credit card users. Earlier Wednesday, Clinton was endorsed by Sen. Patty Murray, from the state of Washington.