Women who say they were sexually assaulted by a New York obstetrician are demanding Manhattan District Attorney Cyrus Vance resign over his handling of the case. One of those who's spoken out about the doctor's alleged abuse is Evelyn Yang, wife of Democratic presidential candidate Andrew Yang.

She said in a CNN interview January 16 that Dr. Robert Hadden sexually assaulted her under the guise of conducting an internal exam for her pregnancy at Columbia's NewYork-Presbyterian hospital in 2012.

Hadden was charged in 2014 on allegations of assault involving six women, but prosecutors indicated at the time that they intended to include accusations dating back two decades from more than a dozen others.

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Instead, in 2016 he agreed to plead guilty to two individual counts of criminal sex act in the third degree and forcible touching. In exchange for his guilty plea and forfeiting his medical license, prosecutors dropped all other charges and agreed not to pursue cases related to other alleged victims. The plea deal also included a stipulation downgrading his sex offender status to the lowest level — meaning he is not listed in New York State's online sex offender registry.

Hadden did not serve a day in jail or prison.

The case led to a 2018 lawsuit against Columbia University that initially included 17 women, and now involves dozens more. Two of the plaintiffs said they were assaulted when they were 15 and 16 years old, at their first gynecological examinations. In the lawsuit, Hadden is accused of a lengthy list of sexual abuses, including licking and digitally penetrating his patients' vaginas without gloves, and fondling their breasts and anuses, all under the pretense of performing medical examinations.

At a press conference in front of New York's City Hall Thursday, Marissa Hoechstetter, who has accused Hadden of assaults during her pregnancy with twins in 2012, said Yang's case highlights problems with how Vance's office and Columbia handled the case.

One assault allegation was reported to police about six weeks before Yang's incident. Hadden was handcuffed while at his office and interviewed by police, but allowed to return to work. It would be more than two years before he was indicted.

"Police knew and the D.A. knew and Columbia knew and they let it happen. They let him go back to work," said Hoechstetter, who is the founder of Reform the Sex Crimes Unit, an advocacy group.

New York City Council Member Carlina Rivera said the case fits a pattern that has led to withering criticism of how Vance's office has handled high-profile sexual assault suspects. She pointed to the district attorney's handling of cases involving disgraced media mogul Harvey Weinstein, and the deceased financier Jeffrey Epstein.

Vance's office declined to charge Weinstein in 2015 after model Ambra Battilana Gutierrez wore a police wire to record Weinstein discussing an alleged assault. After dozens of women accused Weinstein of sexual misconduct in explosive media exposés, Vance's office charged him in May 2018 in connection with two other allegations of rape and sexual assault. His trial on those charges is now underway.

In a different case involving Jeffrey Epstein, a judge expressed shock in 2011 when a prosecutor from Vance's office argued that Epstein should have been given the lowest level sex offender status — the same status later given to Hadden.

"Under Cy Vance's leadership, the Manhattan DA's office and specifically their sex crimes unit and special victims bureau failed to protect and fight for survivors against rich, white and powerful men who committed countless sexual assaults. It is time that Cy Vance resign," Rivera said.

In a statement to CBS News, Vance did not address the calls for his resignation, but defended the sex crimes unit, which he said " fights day in and day out for survivors of sex crimes — helping them to obtain justice, vital services, and critical public policy changes — irrespective of the wealth, power, or race of their assailants."

"Our record of success makes clear that our career prosecutors do not shrink from the challenge of prosecuting powerful men," Vance said.

He added that he supports the victims of Hadden, calling the doctor a "serial sexual predator."

At the protest Thursday, Hadden's accusers said they want other allegations against the doctor to be given a fresh look by a new prosecutor. Dayna Solomon, who said she was abused by the doctor over the course of nine years as a patient, said Vance had a moral obligation to seek a harsher punishment against Hadden.

"If Cyrus Vance's priority was to protect people he would have taken that moral action that was so painfully clear, and so obvious and so warranted," she said.