Tom Steyer talking with reporters in Sacramento last August. Rich Pedroncelli/Associated PressWASHINGTON — Two of the Democratic Party’s most loyal constituencies, labor and environmentalists, are clashing over an effort to raise tens of millions of dollars for an ambitious voter turnout operation aimed at defeating Donald J. Trump in the November election.
The rift developed after some in the labor movement, whose cash flow has dwindled and whose political clout has been increasingly imperiled, announced a partnership last week with a wealthy environmentalist, Tom Steyer, to help bankroll a new fund dedicated to electing Democrats.
That joint initiative enraged members of the nation’s biggest construction unions, already on edge about the rising influence of climate-change activists. The building-trades unions view Mr. Steyer’s environmental agenda as a threat to the jobs that can be created through infrastructure projects like new gas pipelines.
The dispute, laid bare in a pair of blistering letters sent on Monday to Richard L. Trumka, president of the A.F.L.-C.I.O., underscored the tensions between the two pillars of the Democratic coalition.
For decades, organized labor was among the most powerful forces on the left, financing Democratic candidates and reliably delivering working-class votes, and political foot soldiers, for the party in crucial states and districts.
But with blue-collar white voters shifting to the Republican Party and Democrats growing more reliant on higher-income voters and liberal donors like Mr. Steyer, environmental activists are increasingly muscling out unions.
Nowhere was this more evident than during the tense debate over the Keystone XL oil pipeline, in which President Obama and Hillary Clinton, the likely Democratic presidential nominee, ultimately came down on the side of the environmentalists by opposing a project that some of the so-called hard-hat unions fervently wanted.
The friction is not just confined to the Democratic Party: The labor movement itself is changing. As manufacturing has declined, power has flowed away from the unions representing factory and construction workers and toward public- and service-sector workers. The unions that formed the alliance with Mr. Steyer included the two largest teachers’ unions and the American Federation of State, County and Municipal Employees.
The goal of the new voter turnout “super PAC,” announced last week with an initial goal of raising $50 million, was to ensure that liberal groups did not duplicate their efforts, as had happened in some elections. Some unions were asked to give as much as $1 million. Mr. Steyer, founder of the advocacy group NextGen Climate, announced that he would give $5 million and said it was “highly likely” other unions would participate.
But Mr. Steyer has opposed oil and gas projects like the Keystone pipeline, and the construction unions assailed the A.F.L.-C.I.O.’s willingness to make common cause with him as an abandonment of their members and the federation’s principles.
In one of the two letters sent on Monday, presidents of seven of the nation’s biggest construction unions threatened to boycott the new get-out-the-vote effort, called For Our Future PAC.
“It saddens us that the very labor movement we have fought for and supported for over a century seems to have lost sight of its core mission and has moved away from us and our membership in the interest of headline-grabbing political expediency,” wrote the leaders of the operating engineers, plumbers, elevator constructors, roofers, laborers, plasterers, and heat and frost insulators.
In a separate and even more harshly worded letter to Mr. Trumka, the president of the 500,000-member laborers union, Terry O’Sullivan, called the partnership a “politically bankrupt betrayal” of union members. “We object to the political agenda of the A.F.L.-C.I.O. being sold to a job-killing hedge fund manager with a bag of cash,” he wrote.
Both letters were provided to The New York Times by a labor official who insisted on anonymity.
The schism comes as Mr. Trump, the presumptive Republican presidential nominee, is running a populist campaign that could appeal to some union members, castigating free trade agreements and illegal immigrants while vowing not to cut entitlement spending.
Some of the building-trade unions have already gotten behind Mrs. Clinton, but some labor holdouts remain: The Teamsters, for example, have yet to endorse a candidate. And among rank-and-file workers, Mr. Trump could well outperform Mrs. Clinton with the unions that signed on to the letter, a heavily working-class and white male demographic.
Membership in most private-sector unions has steadily declined, leaving organized labor under pressure to find new ways to demonstrate its influence. Mr. O’Sullivan, in his letter, zeroed in on this challenge.
“Years of financial distress have left the A.F.L.-C.I.O. desperate for cash, and it appears that the answer is to sell out to a billionaire who not only has little or no stake in our movement, our members or their work but who has actively fought against our members’ interest,” Mr. O’Sullivan wrote.
Told of the criticism of Mr. Steyer, an executive at NextGen, Sky Gallegos, underscored the new super PAC’s goals of “preventing climate disaster and promoting prosperity.”
“Our new unified effort will help elect progressive leaders who are committed to a just transition to a clean-energy economy that will benefit working families across the nation,” she said.