mike mcdonough with bloomberg, eswar prasad with cornell university, thank you both. >> thank you veryh. . >> ifill: stay with us. coming up on the newshour: why a major opponent of the iran nuclear deal changed his mind, unleashing musical gifts early in life and the rise of heroin in the heartland of small-town america. but first, tonight we launch a series of conversations on the pros and cons of the contentious debate over the nuclear agreement with iran, which congress has 36 more days to review. deal or no deal. tonight, hari sreenivasan talks to a well respected nuclear expert who just resigned as president of a group which publicly opposes it. >> sreenivasan: gary samore helped establish the advocacy group "united against a nuclear iran" in 2008, before serious negotiations had begun over iran's nuclear program. the goal: strengthen sanctions against tehran in the face of what samore and others believed was a clandestine nuclear program. from 2009 to 2013, samore served as president obama's white house coordinator for arms control and weapons of mass destruction, while serious