(CNN) -- Hillary Clinton's decisive win in West Virginia caused John Edwards to throw his support to Barack Obama, the Illinois senator's aides said.
John Edwards endorsed Barack Obama following Clinton's big win in West Virginia.
Edwards was concerned that the Clinton storyline -- that Obama can't win white, working-class voters -- was becoming too damaging to Obama and the party, aides said.
Obama had been courting Edwards for four months. Since Edwards abandoned his presidential bid in January, he and Obama have talked regularly, Obama said.
As late as Monday, Edwards told CNN's Larry King that he wasn't prepared to make an endorsement.
"What I don't want to do is contribute to the divide," he said. "At least for this moment, I think the reasonable thing for me to do is let voters make their decision."
But Clinton's crushing win in West Virginia on Tuesday highlighted Obama's weakness with working-class white voters, a segment of the electorate that may prove pivotal in November. Watch how the endorsement could affect Obama »
Among white voters without a college degree, Clinton defeated Obama by 50 percentage points. Among white voters making less than $30,000 a year, Clinton's margin of victory was more than 60 percentage points.
Edwards had campaigned on the message that he was standing up for the little guy, the people who are not traditionally given a voice in Washington, and that he would do more to fight special interests.
"The reason I'm here tonight is because the Democratic voters have made their choice, and so have I," Edwards told a boisterous crowd in Grand Rapids, Michigan, on Wednesday. Watch why Edwards picked Obama »
"There is one man who knows in his heart that it is time to create one America, not two, and that man is Barack Obama." Edwards also praised Clinton's candidacy.
Despite trailing in pledged delegates, superdelegates and the popular vote, Clinton has repeatedly said her campaign will keep going. Clinton campaign Chairman Terry McAuliffe said Wednesday that, "We respect John Edwards, but as the voters of West Virginia showed last night, this thing is far from over."
Wednesday's endorsement could help Obama reach the blue-collar voters who have been reluctant to embrace his candidacy. On his flight from Grand Rapids to Chicago, Obama told reporters he has no doubt Edwards will help him in every demographic.
And the signs are beginning to show with Thursday's endorsement by the powerful United Steelworkers Union.
"When the presidential primary contests began last year, our Union felt strongly that because of Senator John Edwards's deep commitment to working people and because of our shared beliefs, he deserved our strong endorsement," the union said in a press release. "Today, by virtue of a unanimous vote of our International Executive Board, we find ourselves once again in agreement with Senator Edwards, this time with his decision last evening to endorse Senator Barack Obama."
The union's leaders took aim with Sen. John McCain's "lock-step commitment to four more years of the broken Bush economy and the broken Bush foreign policies," according to the press release.
Obama also picked up two new superdelegates on Thursday.
Democratic Reps. Henry Waxman and Howard Berman, both major committee chairmen and California superdelegates, endorsed Obama, citing his "ability to unite the country and put and end to eight years of failed Bush policies," according to the Obama campaign.
The recent endorsements come amid a new CNN general election "poll of polls" released Thursday, showing Obama leading McCain by 48 percent to 43 percent. Clinton leads McCain by 48 percent to 44 percent.
The polls were taken May 8-12 and consist of three surveys: Gallup (May 9-13), Quinnipiac (May 8-12), and ABC/Washington Post (May 8-11). The poll of polls does not have a sampling error.
The last general poll of polls, released April 29, showed Obama leading McCain by two percentage points and Clinton leading by one percentage point.
After dropping out of the race, Edwards asked Clinton and Obama to make poverty a central issue in the general election and a future Democratic administration, something both agreed to do.
Edwards released his 19 delegates, and they are free to vote for the candidate of their choice -- and the switch to the Obama is already beginning.
At least six of Edwards' eight pledged delegates in South Carolina will throw their support to Obama following Edwards' endorsement, CNN has learned.
Daniel Boan, Christine Brennan-Bond, Robert Groce, Susan Smith, Mike Evatt and Lauren Bilton announced Thursday they will follow Edwards' lead and pledge their support to Obama at the Democratic National Convention in August. They were all elected as pledged delegates for Edwards following his third-place finish in the South Carolina primary on January 29.
John Moylan, the Columbia attorney who directed Edwards' campaign in the state and now serves as an alternate delegate for Edwards, appeared on CNN's "American Morning" Thursday. He stated his support for Obama and hinted that more members of the Edwards delegation would soon follow.
Bilton appeared on the show alongside Moylan and confirmed she will also support Obama.
Boan, Brennan-Bond and Groce, each reached by phone or e-mail, declared they will switch their commitment to Obama. In a separate e-mail, Moylan confirmed that Smith and Evatt also will move into Obama's camp.
The other two delegates supporting Edwards in South Carolina are Tim Moore and Marilyn Hemingway.
Obama, meanwhile, said he hopes Edwards takes an active role in his campaign, but he declined to speculate about an Obama-Edwards ticket.
As Obama inches closer to the Democratic nomination, there's been renewed talk of a joint ticket with Clinton. Obama has said both Edwards and Clinton would be on his shortlist, but he has repeatedly said it's too early to start talking about it.
Clinton on Thursday was scheduled to campaign in Bath, South Dakota, before heading to California for a fundraiser.
Clinton's campaign is about $20 million in the red. The senator from New York spent Wednesday meeting with her finance team and reaching out to undeclared superdelegates.
Obama was expected to be in Chicago and had a fundraiser scheduled in the evening.
CNN's Suzanne Malveaux, Alan Silverleib, Ed Hornick, Peter Hamby and Beth Rotatori contributed to this report.