RALEIGH, N.C. – Sometimes it’s hard to tell whether John Edwards is running for president of the United States or union president.

Edwards has walked picket lines with hotel workers in Chicago, campaigned for janitorial workers at the University of Miami, and rallied with striking Teamsters at a Sikorsky helicopter plant in Connecticut.

If elected president – of the United States – Edwards promises to go on the White House lawn and proclaim the virtues of organized labor in a way not seen since the days of the political patron saints of the labor movement, Harry Truman and Franklin Roosevelt.

“The greatest anti-poverty movement in American history is the organized labor movement,” Edwards told 1,000 steelworkers union leaders in Cleveland this summer.

The stakes are high for Edwards, who is counting on a spate of key labor endorsements this month that could be a make-or-break moment in his bid for the Democratic nomination.

Though Edwards is regarded as the labor favorite within the Democratic presidential field, unions face a difficult choice: Do they go with Edwards and risk backing someone who has had difficulty gaining traction? Or do they back Sen. Hillary Clinton or Sen. Barack Obama, who also have good labor credentials and are leading in the polls?

“It’s a very tough call for labor,” said Peter M. Francia, author of “The Future of Organized Labor in American Politics” and political science professor at East Carolina University. “If they back a loser, stories will be written that labor doesn’t matter any more.

“Edwards is clearly their guy on the issues. Their hearts are with John Edwards. But the only thing holding them back right now is, “Can this guy do it?”‘

Although organized labor has been a declining factor in the American economy, it remains a powerful force in Democratic politics.

Labor’s influence looms in three of the first four Democratic contests. By some estimates, union members account for about one-third of the caucus-goers in Iowa and as much as a quarter of the New Hampshire primary voters. As many as half the caucus participants in Nevada could be union members.

Edwards has an unusual political pedigree for a labor candidate. He comes from North Carolina, one of the least unionized states in the country – a state where political leaders have often been hostile to labor interests.

But the former North Carolina senator has used his working-class background and his subsequent career as a trial lawyer suing corporations to argue that he is uniquely qualified to champion the cause of working people.

Edwards’ father and mother worked in textile mills, although by the time Edwards was a teenager his father had risen to become a plant supervisor for the fiercely anti-union Milliken textile company.

Edwards talks of working summers in his father’s textile plant, and remembering the devastation caused when the textile plant closed in Robbins, the small working-class town where he grew up.

“When people say to me – why do you want to be president of the United States,” Edwards told the steel workers in Cleveland. “It’s because I was born into a mill family, lived my early years in a mill village. I’ve had every advantage you could have in this country. I want that chance to be there for everyone.”

One of Edwards’ first political breaks occurred in 1998, when the state AFL-CIO endorsed the political neophyte in the Senate Democratic primary over a better-known rival with labor credentials. James Andrews, the N.C. AFL-CIO president said labor could have just as easily backed his opponent, D.G. Martin, but Edwards dazzled the labor leaders with his preparation on the issues, his charismatic delivery and his prospects for winning.

Although the AFL-CIO gave Edwards a 97 percent rating for his Senate voting record on labor issues, such as supporting a reduction in steel imports and requiring federal contractors to pay prevailing wages, Edwards had only modest labor support during his 2004 presidential run.

So shortly after the 2004 election, he set out to build closer ties to organized labor.

Whenever labor leaders asked for organizing help, Edwards was there. David Bonior, Edwards’ campaign manager, estimates that Edwards has attended 200 union organizing events on behalf of 23 international unions since 2005.

Edwards is scheduled to spend parts of Sunday and Monday with labor groups in Iowa and Pittsburgh.

Edwards’ hiring of Bonior, a former U.S. House Democratic whip from Michigan, was significant. Bonior was regarded as labor’s leading voice in Congress for a quarter century and was a professor of labor studies at Wayne State University when he joined up with Edwards. Edwards’ campaign staff is peppered with people with strong ties to labor.

“There has never been a presidential candidate in the history of this country that has engaged himself or herself (with labor) like Edwards has,” Bonior said.

Edwards has developed personal relationships with labor leaders across the country and has written numerous letters to corporate leaders on behalf of labor.

When he spoke to the steelworkers in Cleveland, Edwards reminded them that he had been on the picket line at the Goodyear Tire and Rubber plant in Akron when 15,000 members of the union went on strike across the country last fall.

“It is not enough for politicians to appear before you just when they want your support,” Edwards said. “The question is: Are they with you in your battles? Do they believe in their gut in your cause?”

In his courtship of labor, Edwards has campaigned across the country on behalf of state referendums raising the minimum wage. He has taken detailed positions in support of universal health care, raising the minimum wage and ending poverty.

His agenda includes legislation to make it easier for workers to organize, a ban on hiring permanent replacements for strikers, and stricter enforcement of trade agreements.

“John Edwards is a great candidate,” James Hoffa, the Teamsters president, recently told a rally in Chicago. “No other candidate has come out with a labor platform.”

Edwards’ populism could be undercut by some of his lifestyle controversies. Speaking last week to the International Association of Machinists and Aerospace Workers in Florida, Edwards was asked how he could ask the American people to sacrifice while he lives in a 29,000-square-foot house outside Chapel Hill.

“I have no apologies whatsoever for what I’ve done with my life,” Edwards said to loud cheers, according to the Associated Press. “My entire life has been about the same cause, which is making sure wherever you come from, whatever your family is, whatever the color of your skin, you get a real chance to do something great in this country.”

While labor may like Edwards, he has not yet closed the deal with some leaders.

Edwards recently drew a large, enthusiastic crowd at a union hall of the International Brotherhood of Electrical Workers in Cedar Rapids, Iowa.

“His message is on target around here,” said Bill Hanes, a staffer with the local IBEW who is supporting Edwards. “But labor has not made up its mind. If you go to six different locals, each would have a favorite. . . . All the labor unions around here are still looking.”

Last week, the International Association of Firefighters backed Connecticut Sen. Chris Dodd and the United Transportation Union and the machinists and aerospace workers union Clinton. Edwards received the support of the 520,000-member United Brotherhood of Carpenters and Joiners of America.

The AFL-CIO, the largest union federation, has decided to sit out the primary, but the individual unions that compose the federation can make endorsements.

Edwards’ best prospects are with the seven unions that broke away from the AFL-CIO in 2005 to form their own federation, Change to Win. They represent 6 million public employees, health-care workers, Teamsters, hotel workers, textile workers, carpenters and others.

“I think John Edwards has been a very articulate spokesman for working people,’ said Anna Burger, chairwoman of Change to Win. “He has been willing to stand up and seek justice for workers.”

Berger says when Change to Win leaders meet in Chicago on Sept. 25 they will likely decide whether to collectively endorse a candidate, or whether individual unions should endorse. Five of the seven unions have to agree on a candidate before the federation can endorse.

Although Edwards has deep ties to Change to Win, Burger notes that many of the Democratic presidential hopefuls are labor allies.

“They all have a history,” Burger said, “none quite as strong as John Edwards. It’s a challenge this year. There are different regional interests. It’s a challenge to get to a place to unite us.”

The first major endorsements are likely to be made during the first days of September.

“What you will see over the next several weeks is John Edwards going against Hillary Clinton for endorsements,” Bonior said. “We will end up with the most endorsements made by labor in this race, no question. The extent of how much remains to be seen.”

If Edwards gets only a handful of labor endorsements, as Rep. Dick Gephardt did in the 2004 Iowa caucuses, it might not give him the boost he needs.

“He is pinning his hopes on a message of economic populism,” said Francia, the labor scholar. “He is reaching out and trying to appeal to labor folks. He knows they get their people to the polls. But he’s got to avoid what happened to Gephardt.

“If some of the endorsements go to Hillary Clinton or Barack Obama, he is probably in big trouble.”