U.S. leadership of the International Brotherhood of Teamsters voted this week to withhold an endorsement of Democratic front-runner Hillary Clinton and any other candidate in 2016, a big blow to Democrats, who have counted on union support in national elections since the 1990s. The 26-0 vote came Tuesday during the Teamsters’ general executive board meeting in Charleston, South Carolina, and reflects an erosion of labor union support for Democrats over issues such as the job-creating Keystone XL pipeline project and job-imperiling Trans-Pacific Partnership trade pact.

“It’s long past time for Republicans and Democrats to put aside their differences and work together for the good of our country,” Jim Hoffa, the Teamsters Union president, said in a statement released Wednesday. “The Teamsters will work with and support any candidate who puts the needs of America’s working families above the deep pockets of their corporate donors.”

The union said it still looks forward to meeting with Clinton, Vermont Sen. Bernie Sanders and any other candidates “regardless of party affiliation,” according to its statement. The Teamsters also left the door open to Vice President Joe Biden, should he decide to join the 2016 race.

Several conservative media outlets reported the Teamsters also sought a meeting with Republican front-runner Donald Trump. But union spokesman Galen Munroe declined Wednesday to comment when asked about those reports.

The Teamsters union’s anti-endorsement decision was likely to shock the Democratic Party establishment. The union backed Barack Obama in 2008 and 2012 but previously supported the campaigns of GOP Presidents Ronald Reagan and George H.W. Bush. During the 2012 election cycle, the union contributed more than $4.4 million to pro-labor candidates and political action committees, according to data kept by OpenSecrets.org.

Clinton’s relationship with labor unions has been contentious since she launched her White House bid in April. Richard Trumpka, leader of the AFL-CIO public employees union, warned in September that unions would sit out the 2016 campaign over Clinton’s support for TPP, which unions have strongly opposed. The National Nurses Union endorsed Sanders in August.