Next week's Democratic debate could lose its frontrunners.

Loyola Marymount University in Los Angeles is currently facing a union boycott against its food service provider Sodexo — the two sides have been in talks for a deal since March. And with the Dec. 19 debate scheduled to take place at Loyola Marymount, four candidates, including three at the top of the polls, say they won't be there.

Sen. Bernie Sanders (I-Vt.) was the first candidate to recognize the conflict at Loyola Marymount, tweeting Friday that he would not cross the Unite Here Local 11 picket line organized against Sodexo.

I stand with the workers of @UniteHere11 on campus at Loyola Marymount University fighting Sodexo for a better contract. I will not be crossing their picket line. — Bernie Sanders (@BernieSanders) December 13, 2019

Sen. Elizabeth Warren (D-Mass.) soon tweeted that she also wouldn't cross the union's picket line "even if it means missing the debate." Andrew Yang, the underdog tech entrepreneur who was the last candidate to make the stage, said the same, and then former Vice President Joe Biden joined in. Former Housing and Urban Development Secretary Julián Castro, who didn't make this Democratic debate, then called on the remaining candidates to drop as well.

The Democratic National Committee has already faced a union challenge to this debate, deciding in early November to pull it from UCLA over the American Federation of State, County, and Municipal Employees' three-year boycott on speakers at the school. It announced it was moving to Loyola Marymount a few days later. Kathryn Krawczyk