"In a further blow to Senator Hillary Clinton's faltering campaign, former US presidential candidate, John Edwards has endorsed Barack Obama's White House bid, a move that is likely to dramatically boost the frontrunner's stakes among unionised workers.
Mr Edwards, a former Senator from North Carolina and the vice-presidential candidate in 2004, had been backed by several major unions, including the steelworkers' union. He also won respect in poorer communities for his unstinting efforts to tackle poverty in America.
Until he pulled out of the Democratic primary race in January, Senator Edwards had been attracting a very solid share of blue-collar males.
It is among this demographic where Senator Obama has struggled, leading Senator Clinton to crow that she is the stronger candidate because she wins the lion's share of these votes and can deliver swing states like Pennsylvania, Ohio, West Virginia and Michigan.
Mr Edwards appeared with Senator Obama at a rally at Grand Rapids, Michigan - one of those key states which has suffered because of the downturn in US manufacturing.
To the strains of Bruce Springsteen, Mr Obama introduced him as "one of the greatest leaders of the Democratic Party".
Senator Edwards said he had decided to endorse Senator obama because "Democrat voters have made their choice - and so have I".
"There is one man who knows that it is time for a bold leader; there is one man who knows it's time to bring about bold change; there is one man who knows its time to create one America. That man is Barack Obama," he said.
"No matter who your family is, no matter the colour of your skin ... that one America will be achieved under president Barack Obama starting in January 2009!" he said.
Before announcing his decision, he lavished praise on Senator Clinton, saying her fierce campaign had helped the Democrats.
"She cares deeply about working men and women ... she is a woman who is made of steel. She is a leader in this country, not because of her husband but because she has stood up for causes she believed in," he said
"I am so grateful,"Senator Obama said. "I want to thank John for everything he has done to make us one America."
Mr Edwards would bring an impeccable network of contacts as well as 19 pledged delegates to Senator Obama's side of the ledger.
He is now likely to have a clear majority of pledged delegates after next Tuesday's primary."
Anne Davies is the Herald's Washington Correspondent
Please fill me in. This seems like a strong endorsement indeed. Is it what Obama needs to swing many of those in the blue collar group that he has apparently so far failed to do?
Do you think Edwards will be his VP or has Edwards previosuly ruled this out. From what little I have seen of Edwards I must say he appeared a genuine man! It must be another kick in the teeth for Hillary!
