The debate is scheduled to take place on Nov. 20 at the expansive complex.
Ocasio-Cortez, who was a volunteer organizer on Sanders’ 2016 presidential campaign, is expected to formally announce her endorsement at a rally in Queens, New York, on Saturday.
Castro was the first candidate to mention Atatiana “Tay” Jefferson, the 28-year-old Black women killed by a white Fort Worth police officer over the weekend during a welfare check of her home.
Gabbard said the DNC's polling methods lack transparency, and denounced the debates as "commercialized reality television."
Texas State Rep. Briscoe Cain's tweet, quipping "My AR is ready for you" was ultimately taken down, with Twitter saying it violated its standards on threats and violence.