Democrats vying to challenge President Bush in 2004 are first going through a pre-primary before organized labor.

The nine contenders played to labor leaders in the AFL-CIO's presidential forum Tuesday night, offering ambitious plans for health care coverage and restrictions on trade agreements, and criticizing the Bush administration for plans to change overtime pay regulations.

Many eyes were on Dick Gephardt (search), who has staked his presidential aspirations on support from organized labor. His challenge is to convince skeptical leaders of the large service and public sector unions that he is a viable candidate.

Union presidents will formally discuss the AFL-CIO's endorsement plans in a closed session Wednesday.

Leaders say the likely decision will be to schedule another meeting in October to allow more time for consideration.

Gephardt is the only candidate who could obtain a laborwide endorsement, should it be granted, labor leaders acknowledge.

"There's only one issue here: Dick Gephardt," said Andrew Stern, president of the Service Employees International Union (search), the largest in the federation. "Dick Gephardt has the greatest and most passionate labor support of any candidate. The question is how broad is that support."

So far, it's 11 unions with more than 3 million members.

An AFL-CIO (search) endorsement sets a difficult benchmark - two-thirds support from representatives of the federation's 13 million-plus members. Only two candidates have won it before: Al Gore and Walter Mondale.

Gephardt, whose introduction garnered the loudest applause Tuesday, reminded the forum's 2,000 union member audience that he has been a longtime labor ally.

"I've simply tried to represent people like my parents, the people that make this country great, like you," he said, saying his father drove a milk truck and was a Teamster, and his mother was a secretary.

But other candidates want to deny Gephardt the AFL-CIO endorsement, and they used the forum to show that they too were friends of labor.

"My father worked in a mill all his life. I was the first person in my family to go to college," said North Carolina Sen. John Edwards. "And when I was young I myself worked in the mill with my father."

Massachusetts Sen. John Kerry had a tough night with a hoarse voice. He has generated a lot of interest from SEIU and another large, powerful union, the American Federation of State, County and Municipal Employees, and is the likely candidate to deny Gephardt the AFL-CIO prize.

He told the union officials and other Democrats why he thinks he has the best chance to beat Bush.

"I cannot wait to stand up and remind him that having a skilled Navy pilot land you on an aircraft carrier in a borrowed suit does not make up for losing 3 million jobs," said Kerry, a decorated Vietnam War veteran.

Connecticut Sen. Joe Lieberman continued his pitch to moderate Democrats, taking some unpopular stands with the liberal, union audience. He was booed at one point for saying he would support a pilot vouchers program to send poor children to private schools.

"I'm going to speak the truth. I'm going to say what I think is best for America regardless," he countered.

Ohio Rep. Dennis Kucinich hammered all the candidates, citing their mixed records on issues such as free trade and Social Security.

Al Sharpton arrived late and joined his eight rivals on stage with the forum already under way. "I had a nonunion cab driver," he quipped.