WASHINGTON (AP) — All the Democratic presidential candidates slated to participate in next week's debate threatened Friday to skip the event if an ongoing labor dispute forces them to cross picket lines on the campus hosting it.

A labor union called UNITE HERE Local 11 says it will picket as Loyola Marymount University hosts Thursday’s sixth Democratic debate of the cycle, and Massachusetts Sen. Elizabeth Warren and Vermont Sen. Bernie Sanders responded by tweeting they wouldn’t participate if that meant crossing it. Former Vice President Joe Biden, Mayor Pete Buttigieg of South Bend, Indiana, Minnesota Sen. Amy Klobuchar, environmental activist Tom Steyer and businessman Andrew Yang followed suit.

“The DNC should find a solution that lives up to our party's commitment to fight for working people. I will not cross the union's picket line even if it means missing the debate,” Warren tweeted.

Sanders tweeted, “I will not be crossing their picket line,” while Biden tweeted: “We’ve got to stand together with @UNITEHERE11 for affordable health care and fair wages. A job is about more than just a paycheck. It's about dignity.” The other candidates used Twitter to post similar sentiments.

UNITE HERE Local 11 says it represents 150 cooks, dishwashers, cashiers, and servers working on the Loyola Marymount campus. It says it has been in negotiations with a food service company since March for a collective bargaining agreement without reaching a resolution and “workers and students began picketing on campus in November to voice their concern for a fair agreement. The company abruptly canceled scheduled contract negotiations last week.”

“We had hoped that workers would have a contract with wages and affordable health insurance before the debate next week. Instead, workers will be picketing when the candidates come to campus,” Susan Minato, Co-President of UNITE HERE Local 11, said in the statement.

The Democratic National Committee, which organizes its party’s presidential debates, said it and school officials weren’t made aware of the issue until the union’s statement and was looking into the matter.

Loyola Marymount said that it is not a party to the contract negotiations but that it had contacted the food services company involved, Sodexo, and encouraged it “to resolve the issues raised by Local 11."

“Earlier today, LMU asked Sodexo to meet with Local 11 next week to advance negotiations and solutions. LMU is not an agent nor a joint employer of Sodexo, nor of the Sodexo employees assigned to our campus," the university said in a statement. “LMU is proud to host the DNC presidential debate and is committed to ensuring that the university is a rewarding place to learn, live, and work."

This is the second location site set to host the December debate. In October, the DNC announced it wouldn’t be holding a debate at the University of California, Los Angeles because of “concerns raised by the local organized labor community” and was moving the event to Loyola Marymount.

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