Next week's Democratic debate is in jeopardy after all seven candidates who qualified said Friday they would not cross a picket line at the California university where the event is set to take place.

Sen. Elizabeth Warren of Massachusetts was the first candidate to publicly say she would not attend the debate if the labor dispute at Loyola Marymount University continued.

Sen. Bernie Sanders of Vermont, entrepreneur Andrew Yang, Vice President Joe Biden, Mayor Pete Buttigieg, Sen. Amy Klobuchar and billionaire Tom Steyer quickly followed suit Friday afternoon.

The Democratic National Committee, which organizes and sponsors the debates, did not immediately respond to a request for comment. The committee last month moved the debate from the University of California, Los Angeles to Loyola Marymount because of a labor dispute between UCLA and a local union.

But Loyola Marymount is involved in a labor dispute of its own. The university subcontracts with the company Sodexo for its food services operations, and some 150 Sodexo employees work on campus as cooks, dishwashers, cashiers and servers. The workers have been locked in a labor dispute with the company since March and have not yet reached a collective bargaining agreement. Workers and students began picketing on campus in November, according to Unite Here Local 11, the union that represents the workers. The company canceled negotiations scheduled for the first week of December, the union said.

The candidates were sent a letter from the union Friday morning informing them that the workers would be picketing on the evening of the debate.

The union "is fighting for better wages and benefits – and I stand with them," Warren tweeted early Friday afternoon, adding that the Democratic National Committee should "find a solution that lives up to our party's commitment to fighting for working people."

"I will not cross the union's picket line even if it means missing the debate," Warren said.

Sanders also voiced support for the union.

"I stand with the workers ... on campus at Loyola Marymount University fighting Sodexo for a better contract," Sanders tweeted Friday afternoon. "I will not be crossing their picket line."

Yang, who has seen his poll numbers rise in recent months, echoed Warren and Sanders and said he would not cross the picket line to attend the debate.

"We must live our values and there is nothing more core to the Democratic Party than the fight for working people," Yang tweeted .

Soon after, Biden also said he "won't be crossing a picket line."

"A job is about more than just a paycheck. It's about dignity," Biden tweeted.

Buttigieg and Steyer said the same on Twitter. Klobuchar announced at a campaign event that she would not, adding that the DNC should move the debate.

The DNC did not immediately respond to a request for comment. The committee last month moved the debate from the University of California, Los Angeles to Loyola Marymount because of a labor dispute between UCLA and a local union.

Susan Minato, co-president of Unite Here, said workers would be picketing at the university at the time of the debate.