Sen. Bernie Sanders, I-Vermont, expressed his support for undergraduate and graduate student teaching research assistants’ efforts to unionize at Columbia University. 

Sanders sent a letter to students saying he hoped they would vote to join the United Auto Workers and recalled meeting with a few students who were pushing to unionize.

“Having a union ends the arrangement where the employer makes all the decisions unilaterally, and institutes a legal process where your union organization collectively bargains with the employer,” Sanders said in his letter, according to the Columbia Spectator.

Sanders is the latest progressive politician to endorse the move, with New York Mayor Bill de Blasio also supporting the effort.