"With our convictions and a little backbone we will take back the White House in November," said Edwards, ending his second campaign in a hurricane-ravaged section of New Orleans where he began it more than a year ago.

Edwards said Clinton and Obama had both pledged that "they will make ending poverty central to their campaign for the presidency."

"This is the cause of my life and I now have their commitment to engage in this cause," he said before a small group of supporters. He was joined by his wife Elizabeth and his three children, Cate, Emma Claire and Jack.

It was the second time Edwards sought the Democratic presidential nomination. Four years ago he was the vice presidential running mate on a ticket headed by John Kerry.

Four years later, he waged a spirited, underfunded race on a populist note, pledging to represent the powerless against the corporate interests.

He finished second in the Iowa caucuses that led off the campaign, but he was quickly overshadowed -- a white man in a race against the former first lady and a 46-year-old black man, each bent on making history.

Edwards said that on his way to making his campaign-ending statement, he drove by a highway underpass where several homeless people live. He stopped to talk, he said, and as he was leaving, one of them asked him

"Well I say to her and I say to all those who are struggling in this country, we will never forget you. We will fight for you. We will stand up for you," he said, pledging to continue his campaign-long effort to end what he frequently said was "two Americas," one for the powerful, the other for the rest.

The former North Carolina senator did not immediately endorse either Clinton, seeking to become the first female president, or Obama, the strongest black candidate in history.

Both of them praised Edwards -- and immediately began courting his supporters.

"John Edwards ended his campaign today in the same way he started it -- by standing with the people who are too often left behind and nearly always left out of our national debate," Clinton said.

Obama, too, praised Edwards and his wife. At a rally in Denver, he said the couple has "always believed deeply that two Americans can become one, and that our country can rally around this common purpose," Obama said. "So while his campaign may have ended, this cause lives on for all of us who still believe that we can achieve that dream of one America."

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.

Edwards amassed 56 national convention delegates, most of whom will be free to support either Obama or Clinton.

As expected, Edwards said he was suspending his campaign rather than ending it, but aides said that was simply legal terminology so that he can continue to receive federal matching funds for his campaign donations.

An immediate impact of Edwards' withdrawal will be six additional 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.

Edwards won 26 delegates in the Iowa, New Hampshire and South Carolina contests. Under party rules, 10 of those delegates will be automatically dispersed among Obama and Clinton, based on their vote totals in those respective contests. The remaining 16 remain pledged to Edwards, meaning his campaign will have a say in naming them.

Three superdelegates -- mainly party and elected officials who automatically attend the convention and can support whomever they choose -- had already switched from Edwards to Obama before news of Edwards' withdrawal from the race.

Edwards waged a spirited top-tier campaign against the two better-funded rivals, even as he dealt with the stunning blow of his wife's recurring cancer diagnosis. In a dramatic news conference last March, the couple announced that the breast cancer that she thought she had beaten had returned, but they would continue the campaign.

Their decision sparked a debate about family duty and public service. But Elizabeth Edwards remained a forceful advocate for her husband, and she was often surrounded at campaign events by well-wishers and emotional survivors cheering her on.

The campaign ended as it began 13 months ago -- with the candidate pitching in to rebuild lives in a city still ravaged by Hurricane Katrina. Edwards embraced New Orleans as a glaring symbol of what he described as a Washington that didn't hear the cries of the downtrodden.

Edwards burst out of the starting gate with a flurry of progressive policy ideas -- he was the first to offer a plan for universal health care, the first to call on Congress to pull funding for the war, and he led the charge that lobbyists have too much power in Washington and need to be reigned in.

The ideas were all bold and new for Edwards personally as well, making him a different candidate than the moderate Southerner who ran in 2004 while still in his first Senate term. But the themes were eventually adopted by other Democratic presidential candidates -- and even a Republican, Mitt Romney, echoed the call for an end to special interest politics in Washington.

Edwards' last primary was in his home state of South Carolina last week. He finished a poor third, wining only his home country, his victory in the 2004 race a distant memory.