MSNBC and NBC News dismissed the veteran political journalist Mark Halperin on Monday, joining several other organizations that have also severed ties with him after a group of women came forward last week to accuse him of sexual misconduct.

Mr. Halperin’s contract with MSNBC and NBC News has been terminated, a spokesman at MSNBC said in an email on Monday, three days after the “Game Change” author apologized for the “aggressive and crude” behavior he had exhibited while working at ABC News more than a decade ago.

A celebrity among political reporters, Mr. Halperin joined ABC News in 1988 after graduating from Harvard University, working his way up from an entry-level position as a desk assistant and rising through the ranks to become political director in 1997. During that time he also garnered acclaim for his widely read politics newsletter, The Note.