Analysts: Kerry's Obama Endorsement Latest Blow to Edwards

"Barack Obama can be, will be and should be the next president of the United States," Kerry, a Massachusetts senator, said at a rally in Charleston, S.C.

Edwards was Kerry's vice presidential running mate in 2004. Despite their political alliance, the two men weren't close personally and differed behind the scenes on campaign strategy during a race they lost to President George W. Bush and Vice President Dick Cheney.

"There's been some bickering back and forth between Kerry and Edwards about who did what during the campaign," said Rob Christensen, a political columnist for The News & Observer newspaper in Raleigh.

The endorsement came in Edwards' native state, and the former senator from North Carolina also was making a campaign appearance in Charleston.

"The timing is very damaging to Edwards because it comes in South Carolina, where Edwards may be making his last stand," Christensen said.

A new poll out of South Carolina shows Obama, a senator from Illinois, garnering the support of 42 percent of likely Democratic voters. New York Sen. Hillary Clinton polled at 30 percent of the voters, while Edwards trailed at 15 percent.

Obama and Clinton split primaries in Iowa and New Hampshire, and Edwards has pegged South Carolina as important to his campaign. He won the state in 2004, his only primary victory.

Edwards responded to Kerry's move by saying that he respected the decision and announcing that more than 80 "state and local community leaders" in South Carolina had endorsed his campaign.

“I continue to believe that this election is about the future, not the past, and that the country needs a president who will fight aggressively to end the status quo and change the Washington system and to give voice to all of those whose voices are ignored in the corridors of power,” he said.

North Carolina State University political science professor Andrew Taylor said Edwards has much bigger problems than Kerry's endorsement of a rival. Obama and Clinton appear to be pulling in the African-American vote that helped Edwards four years ago.

"It's got to hurt in the stomach and the heart, but does it really make that much difference? Probably not," Taylor said of the endorsement. "It's a very different kind of equation in 2008 than it was in 2004."

Christensen said Edwards' losing the powerful casino labor endorsement in Nevada to Obama is more damaging than Kerry's turn. The challenge for Edwards now is remaining relevant, he said.

"The helium is coming out of that balloon, and he's losing altitude by the hour. Edwards is in big trouble right now," Taylor said.