CHICAGO, Aug. 5 ・All but one of the nine Democratic presidential candidates made extravagant bids for support from organized labor here tonight, calling for expanded health care coverage and some restrictions on free trade policies and denouncing the Bush administration for cutting funds to state governments.

The candidates squabbled over how ambitious health care programs should be and how restricted trade policies should be. But for the most part, they largely endorsed the views held by organized labor as they appeared at a 90-minute forum sponsored by the A.F.L.-C.I.O.

Their appearance came as one of them, Representative Richard A. Gephardt of Missouri, struggled to win the support necessary to gain the organization's endorsement, a critical aspect of his nomination strategy. Union leaders said today that his hope of achieving that continued to be distant, since it required him to win the support of locals representing two-thirds of the federation's 13.5 million members.

Still, Mr. Gephardt, the former House minority leader, received a warm ovation as he reminded A.F.L.-C.I.O. leaders of his support of their positions in Congress and roared his denunciation of President Bush ・so loudly that Senator John Edwards of North Carolina, standing on Mr. Gephardt's right, visibly recoiled.

"This administration has declared war on the middle class in this country; 83,000 jobs have been lost a month," Mr. Gephardt said, adding, "He's got the worst record since Herbert Hoover. He has got to go so we can get jobs back."

The event tonight, before 2,000 people in a hall on the Navy Pier, which juts into the shores of Lake Michigan, was the latest in a blur of debates and forums that the candidates have attended. This one was hampered by a bulky format that made it difficult for the candidates to draw many contrasts among them.

On several occasions, Representative Dennis J. Kucinich of Ohio, appeared frustrated as he challenged his opponents to promise, as he did, "as my first act in office" as president to repeal the Nafta deal with Mexico and Canada, which was passed under President Bill Clinton in 1993 and was strongly opposed by union leaders. Other candidates ignored Mr. Kucinich's entreaties as the debate moderator, Bob Edwards of National Public Radio, slid into the round of questions.

Still, even this format provided insights into the candidates and their strengths as they prepare for a shift to a fierce schedule after Labor Day.

Senator Joseph I. Lieberman of Connecticut, who has portrayed himself as the most centrist candidate, sought to stand out tonight as he refrained from offering unabashed endorsements of union positions.

At one point, the senator was booed when he said he would establish a pilot program to provide poor students with vouchers to attend private schools, a position strongly opposed by teacher unions.

"I'm going to speak the truth," Mr. Lieberman said. "I'm going say what I think is best for America regardless. This is an experiment. Try it for three to four years, limit it to poor children, don't take any money out of public school budgets."

Senator John Kerry of Massachusetts had a second difficult night at a televised Democratic forum. As had occurred at a debate in South Carolina in May, he struggled with a hoarse, scratchy voice, a distraction from what his aides had hoped would be a commanding performance.

Mr. Kerry coughed and cleared his voice as he recited a detailed list of pay packages given to executives at corporations like Honeywell and Lucent. "My friends, that's trickle-down economics, and I believe every worker in America is tired of being trickled on by George W. Bush," he said.

Carol Moseley Braun, the former Illinois senator, attacked Mr. Bush for favoring the rich. "Greed has driven the economic policy of this administration," she said. The administration's approach to economics, she said, "does not work, has not worked, is not working."

The Rev. Al Sharpton of New York arrived late but offered a quick excxuse. "I had a nonunion cab driver," Mr. Sharpton said.

Mr. Kucinich and Mr. Gephardt were the most direct in professing their support for labor's goals. Mr. Gephardt noted that he had voted against Nafta in Congress and that others on stage ・among them, Mr. Kerry, Senator Bob Graham of Florida and Howard Dean, the former governor of Vermont ・had supported the trade pact, even as they expressed reservations about that support in the course of a Democratic nomination process where labor plays a critical role.

"I appreciate the position that some take here, and I appreciate what they are saying," Mr. Gephardt said. "But I have just one thing to say to you: Check our records. Check out who was there when the fat was on the fire and we had to fight our own president."

Mr. Graham at one point seemed about to break with the orthodoxy of the evening on trade. "I know what I'm about to say may not be popular with everyone in this room," he said. "The fact is that the United States does not have a choice to become a protectionist nation."

But, Mr. Graham said, as president, he, too, would make sure that any trade pacts included provisions for "labor rights, human rights and environmental standards."

The appeals for support went beyond the issues, with candidates invoking their personal backgrounds as they sought to bond themselves with the labor movement.

Looking out at the hall of workers, Mr. Edwards noted that his father was a mill worker, his brother is a member of the International Brotherhood of Electrical Workers, Local 553, and his mother is a retired member of the postal workers' union.

Mr. Gephardt noted that his mother, who died eight weeks ago, spent her life as a secretary and his father drove a milk truck. If elected, he vowed, "every day on every issue, I'm going to try to figure out how to take care of people like my parents."

On health care, Mr. Lieberman called for incremental changes to expand coverage, drawing a clear contrast with the ambitious program proposed by Mr. Gephardt. "If we try to do this all at once as much as some propose, we're going to spend our country as much into debt as George Bush's tax cuts," he said.

Mr. Kerry responded: "I believe that America deserves a bigger, bolder more realistic vision than the one that Joe just described to you."

For his part, Dr. Dean warned about efforts by the administration to restrict the ability of union workers to organize. "What we have to do is let the American people understand that if you want a strong economy, the right to organize is important because you have to make sure middle-class people have enough money in their pockets," he said.