Nikki Haley just destroyed her credibility and her political future with her “craven and cynical” endorsement of Donald Trump. Toward the end of her own primary campaign, the former South Carolina governor became a vehement critic of the ex-president for whom she had served as United Nations ambassador, and while she still draws a sizable portion of the anti-Trump vote despite dropping out the race, she threw her support behind the presumptive GOP nominee. “As you know, I was out there [on the campaign trail],” Heilemann told “Morning Joe.” “I listened to her as she got tougher and tougher on …