In what could be a huge blow to Democratic presidential hopeful Hillary Clinton, the AFL-CIO’s political committee is expected Wednesday to recommend the union delay endorsing anyone.

Hillary has had a tough time gaining union support while running for president. This despite her being the frontrunner for the Democratic party. Much of the hesitance stems from President Barack Obama’s recent efforts on trade.

Unions, hoping to make the Trans-Pacific Partnership (TPP) an important campaign issue, have put pressure on Hillary to take a firm stance against the trade agenda. After a long delay, all unions got from her was a request for the president to work better with Democratic lawmakers.

According to sources for Reuters, the political committee voted last week to recommend the union delay endorsing anyone. The committee is expected make the recommendation to union leadership during its executive council gathering in Maryland between July 29-30. During the gathering union leadership is also expected to meet privately with Hillary as well as her Democratic rivals Sen. Bernie Sanders and former Maryland Gov. Martin O’Malley.

Unions wield considerable political influence and tend to contribute significantly to Democratic campaigns. If enough unions decide not to officially endorse Hillary or even just delay doing so, it could be devastating for her campaign.

Many within the labor movement have already given up on her. Outgoing Communications Workers of America President Larry Cohen joined many smaller unions earlier in the month and endorsed Sanders. The self-proclaimed socialist has made worker rights and labor issues a central focus of his campaign. Cohen even said he plans to volunteer for his campaign.

AFL-CIO President Richard Trumka, however, has warned against endorsing Sanders. This despite his own union’s hesitance towards Hillary. In early June he sent a memo to the leaders of associated unions telling them not to endorse Sanders.

Despite not yet demonstrating a strong position on trade, Hillary has still tried in other ways to court unions. She prominently showed off union-made gear in May during the official launch of her online campaign shop, and she urged people to stand firmly for unions during a speech in Chicago.

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