"It's expending a huge amount of political capital, and labor is not going to be well-positioned to achieve their other priorities," said Marick F. Masters, a labor expert who is director of the Center for Workplace at Wayne State University in Michigan.
"They will be yelling in a forest -- nobody can hear them," Masters said.
A Gallup Poll out last week found a drop in public support for labor unions, with a slight majority now saying they hurt the economy. Only 48 percent of respondents said they "approve" of labor unions -- down 11 points from a year ago.
Unions haven't been held in such low standing by the public since Gallup first started asking that question in 1936.
Labor unions have seen their membership decline for decades. About a third of voters were from union households in 1976; that number was down to 21 percent last year, according to exit polls. Union membership did, however, rise significantly in 2008, adding 428,000 members.
Labor leaders see the current debate in Washington as a chance to achieve vast health-care expansions that would help their members. They also sense an opportunity to crack down on health insurance companies that have tangled with unions over the years.
"We see this up-close and personal every day. Our workers see this on the front lines," said Anna Burger, secretary-treasurer of the Service Employees International Union, and the chairwoman of the Change to Win coalition.
"It's at the top of the agenda -- it needs to get done," Burger said. "It's important to the Obama administration, and it's important to the Democratic agenda."
Despite their differences, Change to Win and the AFL-CIO agree that, soon after health care is finished, Congress should take up the Employee Free Choice Act (EFCA), a controversial measure that would make it far easier for workers to unionize.
"I anticipate it being the next thing up," Burger said.
But EFCA -- called "card-check" by its opponents -- was facing uncertain legislative prospects even before the health-care debate got bogged down this summer. Quick passage of the measure seems unlikely, particularly as labor unions continue their focus on health-care reform.
"They're trying to bully and coerce, while most Americans are scared to death of putting us on a path to socialized medicine," said Katie Packer, executive director of the Workforce Fairness Institute, a business-backed group that's opposing EFCA.
Trumka and other labor leaders downplay talk of the health-care debate as a test of their political sway.
"Y'all always want to make this about a litmus test for us -- this isn't about us. This is about the American public," Trumka told reporters last week. "This is about the American people and what they want, and we're speaking up for what they've told us they want."
But labor has put itself on the line, as public anger bubbles up in the health care debate, said Masters, the labor expert.
"As a political diagnosis, both the Democrats and organized labor have paid a tremendous price for health care," he said. "They've boxed themselves in."