The journalist has been suspended from his role as a MSNBC contributor, while a follow-up to 2010's "Game Change" was canceled by Penguin Press and HBO dropped plans for a miniseries based on the book about the 2016 election.
The four women, who were not identified in the CNN report, said the encounters took place between the late 1980s and 2006, during which time Halperin worked at ABC News in influential positions including political director.
Mark Halperin, center, during a panel discussion of the second season of the Showtime documentary series "The Circus" at The Newseum in Washington on May 3. "I acknowledge that, and I deeply regret it", he said in the post.
Halperin has apologized for his behavior and said he sought counseling.
"No one had filed a human resources complaint against me, no colleague had confronted me", he said on Twitter.
The peacock network, which had benched Halperin in the immediate wake of the sexual misconduct allegations, was the last of the media companies with which he'd had relationships going into last week to completely cut ties with him. He then admitted that that while no one reported him to HR, he didn't need that push "to know that I was a selfish, immature person, who was behaving in a manner that had to stop".
"I'm angry because I was silent, and because I was silent this happened to other people", she said.
The women's accounts ranged from Halperin propositioning them for sex to nonconsensual groping. "But I realize that's a small point in the scheme of things", he said.