A letter signed by more than 50 former staffers of Rep. Eric Swalwell described recent allegations of sexual assault and misconduct against him as “serious” and “credible,” while demanding he resign from Congress and drop his bid for California governor.

“The allegations reported by the San Francisco Chronicle and CNN are serious, credible, and demand accountability,” the letter said. “We stand unequivocally with our colleague, who showed extraordinary courage in coming forward to share her truth. We believe her.”

It comes two days after both CNN and the Chronicle reported that a former staffer accused the California Democrat of sexual assault, describing a night of drinking that ended with Swalwell having sex with her when she could not consent. In addition, three other women who spoke with CNN alleged other sexual misconduct by Swalwell, including sending unsolicited nude photos and graphic messages.

The Manhattan District Attorney’s Office said Saturday it is investigating an allegation of sexual assault against Swalwell. It encouraged survivors and those with knowledge of allegations to contact its Special Victims Division.

Current Swalwell staffers separately released an unsigned letter on Saturday calling the allegations against Swalwell “abhorrent,” while asking for understanding toward staffers who did not immediately resign from their jobs.