The president of the biggest labor organization in America says this is "a defining Labor Day for working people."
It's the turn into the home stretch of a congressional campaign that looks truly grim for labor's traditional ally -- the Democratic Party. So unions are trying to stir up their members and money, but they're not having an easy time of it.
AFL-CIO President Richard Trumka laid out the stakes for union workers.
"This election is about economic patriots, and it's also about corporate traitors," Trumka said. That harsh language was aimed at companies that send jobs overseas.
Labor says it's mobilizing in 26 states -- more than 400 contests for seats in Congress and state offices.
One example is a radio spot about raising the minimum wage, for the Senate race in Missouri between Democrat Robin Carnahan and Republican Roy Blunt:
"Congressman Blunt didn't think they deserved a pay raise. Just himself. Congressman Roy Blunt. After 14 years in Washington, he's really out of touch. Paid for by the American Federation of State, County and Municipal Employees."
But business is revved up, too.
Thomas Bell, board chairman of the U.S. Chamber of Commerce, tells members in a blog post to go up this week that no business person can afford to sit this one out.
The Chamber sent strategist Bill Miller out to Missouri.
"I'm here today to announce our formal endorsement of Roy Blunt," Miller said.
Naturally, the endorsement came with TV ads: "While 71 percent of us voted no, Carnahan sided with lobbyists, big unions and Washington insiders to force Obamacare on us."
Labor and business each has its own strengths. For labor, it's people and organization. For business, the strength is money.
Every election cycle, business outspends labor. And those numbers could become even more lopsided.
Political scientist David Magleby of Brigham Young University has tracked outside groups in campaigns for more than a decade.
"The landscape of American campaign finance was changed fundamentally by the Supreme Court decision in Citizens United," Magleby said, referring to the January ruling that lets corporations and unions spend unlimited amounts in campaigns.
Just suppose, says Magleby, that a big corporation decides to play in a hot Senate race. "Drop $12 [million] to $15 million. Well that's a small fraction of their general treasury money or their profits. But it would dwarf what unions or others would likely spend in a race, even if it was a high-priority race."
It's not clear how much corporate and union money is going into politics this fall. Unknown millions go through channels that skirt the disclosure laws.
But organized labor is expected to spend $100 million or more -- a number that's likely to be matched by just two pro-business groups, Club for Growth and the U.S. Chamber, before counting any other business groups or individual corporations.