WASHINGTON - Democrat John Edwards and Republican Rudy Giuliani yesterday dropped out of the presidential races, setting the stage for a national showdown next week between two clear front-runners in each party.
With just five days until more than 20 states vote on Feb. 5, the thinning of the fields makes the two races less chaotic and offers simpler choices for voters across the country, creating what could be an unprecedented national referendum on presidential nominees.
The withdrawal of Edwards, the former North Carolina senator who rode a populist message of equal parts hope and anger to a robust second-place finish in the Iowa caucuses, weeds the Democratic contest down to two major contenders: Senators Hillary Clinton of New York and Barack Obama of Illinois, each of whom yesterday staked a claim to Edwards's largely working-class constituency.
Needing to make up ground in polls of some large states in which he trails Clinton, Obama yesterday addressed himself directly to Edwards's supporters and ratcheted up his rhetoric.
"Democrats will win . . . not by nominating a candidate who will unite the other party against us, but by choosing one who can unite this country around a movement for change," he said in Colorado. In addition, he accused Clinton of having supported President Bush's national security agenda on Iraq and Iran.
In response, Clinton's campaign accused Obama of abandoning his pledge to create a "new politics" based on positive campaigning. And Clinton herself said she hoped "we could get back to talking about the issues, drawing the contrasts that are based in fact that have a connection to the American people."
The Republican race still has four major candidates, but with Representative Ron Paul of Texas drawing support from a small libertarian faction of the party and former governor Mike Huckabee of Arkansas concentrating on Southern states, supporters of Senator John McCain of Arizona and former governor Mitt Romney of Massachusetts said they are the only candidates running truly national campaigns.
At an afternoon rally in California, Giuliani threw his support to McCain, whose staunch support for the Iraq war and an aggressive foreign policy have matched his own during the campaign. The former New York mayor called McCain "an American hero" and "the most qualified candidate to be commander in chief."
Giuliani's departure from the race - along with his endorsement - could reap immediate dividends for McCain in the form of victories in New York and New Jersey, big states where the winner takes all the delegates.
Last night, McCain scored another coup when he secured the endorsement of California Governor Arnold Schwarzenegger.
Romney, speaking on Fox News, warned conservatives across the country that they must rally to his side or accept the prospect of McCain, who has antagonized many Republicans on immigration and taxes, becoming the party's standard-bearer.
Romney assessed his own ability to stop McCain as "no sure thing at this stage," in part because Huckabee is staying in the race and siphoning off social conservatives. Romney quickly accepted an offer by NBC's "Meet the Press" to host a one-on-one debate between McCain and Romney on Sunday, but McCain declined.
Last night, all four Republicans squared off in a debate at the Ronald Reagan Presidential Library in Simi Valley, Calif., where Romney took aim at McCain as having views that are "outside the mainstream of conservative thought."
McCain responded: "I'm proud of my conservative record. It's one of reaching across the aisle to get things done for the American people."
Earlier in the day, in New Orleans, Edwards brought his campaign to a poignant finish in the same hurricane-ravaged neighborhood where he began it in December 2006. The former senator, whose exhortations to voters to take on the "corporate greed" that underlies the nation's problems went unheeded, nonetheless credited himself with injecting "the voices of working people" into the campaign.
"I've spoken to both Senator Clinton and Senator Obama," he said. "They have both pledged to me, and more importantly through me to America, that they will make ending poverty central to their campaign for the presidency."
Clinton and Obama could gain equally from Edwards's departure. Edwards has said he might endorse someone - and has portrayed himself as more in line with Obama than Clinton. An endorsement of Obama might steer some Edwards supporters to the Illinois senator. But Obama has had trouble attracting working-class voters in the early-voting states, and polls have suggested that Edwards's supporters are more likely to move to Clinton as their second choice.
Linda Fowler, a political scientist at Dartmouth College, said both Clinton and Obama will have to work for the support of working-class white men, who could choose to stay home rather than back either of them.
"My first thought upon hearing Edwards was withdrawing is 'Where is the white male vote going to go?' - and the answer is 'I don't know,' " she said. So far, Democratic turnout has been high across the board, but if some white male voters were to stay home, it could help Obama in Southern states, where he has shown an ability to maximize turnout of black supporters.
Edwards's withdrawal will also change the character of the Democratic debates, she said, where he sometimes worked in tandem with Obama against Clinton.
"Part of what she had going for her in New Hampshire was she had two guys against one gal," said Fowler. "Now it's one on one. Does this make it easier to draw contrasts between them? Or does it mean she will no longer look like the gallant little lady standing up to two guys?"
Fowler noted that Edwards's withdrawal removes some complications in the delegate-selection process, in which Democrats in most states apportion them based on a candidate's percentage of the vote in each congressional district, meaning that sometimes a distant third place can secure delegates.
With only two candidates in the race, the chances of a skewed result are reduced. And with Edwards gone, Obama and Clinton will have a chance to compete for more delegates in states where the former North Carolina senator was strong.
Clinton yesterday took her campaign to the South, attending events in both Georgia and Arkansas, where her husband was governor for 12 years. Her campaign has said it expects to win Arkansas. But Georgia, with a demographic similar to South Carolina's, where she lost last week, will be a much harder sell.
Speaking at a convention in Atlanta of Baptists from around the country, she gave a subdued presentation promising to end what she called an "epidemic of indifference" to social problems over the past seven years.
She did not make any new attacks on Obama, and even hinted that her husband, whose criticism of Obama may have backfired in South Carolina last week, does not always speak for her.
"Bill and I have been talking and debating since we first met 35 years ago," she said. "Sometimes the decibel level can rise. That is how we learn to explore our differences."
Globe staff reporter Michael Kranish contributed to this report. Material from the Associated Press also was used.