With Dick Gephardt's endorsement of John Kerry (search) on Friday, the Massachusetts senator is hoping to win some of the labor support that backed Gephardt before he dropped out of the race for president, but some experts wonder if union backing has the same oomph as it once did.

The percentage of the workforce represented by unions is about one-third of what it was 40 years ago. Private-sector unionization has dropped to 8.5 percent — a fifth of what it was in the 1960s.

"Labor is still the second most important constituency group in the Democratic Party" behind African Americans, said Larry Sabato, director of the Center for Politics at the University of Virginia (search). "Their money and volunteers still matter, but they're on a decline."

Labor groups maintain they still carry political clout and that the numbers don't reveal the truth.

There is a "mutual desire on the part of some of the campaigns ... to talk about our issues and how our issues are going to be treated as this campaign moves forward," said Donald Kaniewski, director of legislation and politics for the Laborers International Union of North America (search).

"We're confident that if we talk about the issues to our members, talk about where the candidates stand on those issues, our members are well capable of making a decision that reflect their own interests," Kaniewski said.

But many labor groups have hit on hard times this nominating season, throwing their support behind Gephardt, who dropped out after finishing fourth in the Iowa caucuses, and Howard Dean (search), the former Vermont governor who has seen his popularity plummet in the past few weeks.

Americans for Economic Justice (search) — a coalition of industrial unions including the Teamsters, United Steelworkers of America, International Association of Machinists and Aerospace Workers, International Association of Iron Workers and the Laborers' International Union of North America — put its chips on Gephardt, and is now looking for a successor to earn its support.

Candidates Kerry, North Carolina Sen. John Edwards (search) and retired Army Gen. Wesley Clark (search), in particular have been discussing a sit-down with the coalition. Though the conversations have not yet transpired, Kaniewski said he expects some heart-to-hearts before the primary battle is over. 

"That does not guarantee the alliance will make any endorsement ... [but] it's something that's necessary to advance our issue agenda to make sure the things Dick Gephardt offered us, like fair trade, don't get lost in the ongoing debate," Kaniewski said.

Several unions, including the Service Employees International Union, the International Union of Painters and Allied Trades and the American Federation of State, County and Municipal Employees, gave their support to Dean.

But since Dean has not yet won a state and is banking his survival on winning Wisconsin on Feb. 17, reports have suggested the doctor-turned-politician may be perilously close to losing his union backing. His labor supporters have reportedly told Dean that he needs to start winning primaries and caucuses if he's going to win the nomination.

"It's difficult when you lose the first two. You go in with high expectations and you get demoralized. You've got to rev up the troops," said Larry Scanlon, political director for the AFSCME.

The SEIU told Fox News last week that it had not given Dean an ultimatum and it would not withdraw its endorsement.

Kerry partisans argue that the split between Gephardt and Dean further weakened big labor's influence and say it's time to unite behind the Massachusetts senator in preparation for a showdown with President Bush in November. Kerry, who utilized high-profile Massachusetts Sen. Ted Kennedy to rally unions to his side, had little union support heading in to Iowa but now has the support of over 2.6 million union workers.

But observers say that support may not go as far as it used to. Less than one-fourth of Iowa caucus-goers were from union households, according to polls conducted for Fox News and other media outlets by Edison Media Research and Mitofsky International. In 2000, one-third of Iowa voters were from union households.

The percentage of voters from union households in last Tuesday's races were: 12 percent in South Carolina; 39 percent in Missouri; 29 percent in Delaware; 21 percent in Arizona; and 21 percent in Oklahoma.

"Labor is not the force it once was in the Democratic Party, though it is still significant," Sabato said. "Anyone who doubts that labor is less influential simply has to remember Iowa when there were two choices — Dean and Gephardt, who finished third and fourth, a poor third and a poor fourth."

"What I do think was surprising was [labor's] inability to deliver for Gephardt in Iowa and also to some extent their inability to deliver for Dean in Iowa," said campaign expert Ron Faucheux of the Faucheux Analysis. "But that doesn't mean people should write off organized labor as a big influence in politics, particularly public employee sectors. If they have a reason to unite in a clear line, then they may be more effective."

Many political observers and media outlets said the inability of unions to get members to show up for Gephardt is the cause for his loss in Iowa. Kaniewski argued the outcome was a result of the unusual caucus process, not because of a lack of influence.

It's "simply not true" that Gephardt lost Iowa because of a labor movement failure, Kaniewski said. "We believe our turnout operation was excellent … our viability forced our members to either go home or go to somebody else."

Labor groups insist they're instrumental in pushing working families' issues on Capitol Hill and on the campaign trail and regardless of whom they support in the primary season — if anyone — their influence will be key come November.

"I think we'll just have to see what happens as the campaign continues," said Candice Johnson, spokeswoman for the Communication Workers of America, which recently endorsed Kerry.

"I'm sure when there's a Democratic nominee, you'll have most of the labor movement — all of the labor movement — supporting that candidate. If you compare any of the Democratic contenders' records against President Bush's record, there's no question who's on the side of working families."

Some labor groups, including those who backed Gephardt, and other supporters of the Missouri congressman, say they won't endorse any candidate until a clear nominee emerges.

"At this point, I will let the people choose for me," said Rep. William Clay, the Missouri Democrat who served as Gephardt's national campaign co-chairman. "The real objective here is to beat President Bush in November and I trust the people to be able to come up with the candidate that can successfully take on Bush and take on the White House for the American people."

Fox News' Carl Cameron and Ellen Uchimiya and The Associated Press contributed to this report.