The AP reports that McGovern, a former Democratic presidential nominee, now believes it is virtually impossible for Clinton to take the nomination.
Clinton campaign spokesman Jay Carson responds to the decision: "We respectfully disagree with Senator McGovern on this and millions and millions of voters agree that this contest should continue."
McGovern is reportedly calling Bill Clinton to make him aware of his decision and says he remains friends with both Bill and Hillary Clinton. The couple worked on McGovern's 1972 campaign. Hillary, then a Yale law student, helped register Latino voters in Texas. Her then boyfriend, Bill, was a Texas organizer for McGovern.