President Trump has disavowed the Iran nuclear deal, and he has threatened to leave it altogether if Congress does not amend it to permanently block Tehran from building nuclear weapons. Today, a top negotiator in the Obama administration talks about how the deal was reached and what it feels like to watch Mr. Trump threaten to undo it. Guests: Jake Sullivan, a negotiator for the Iran deal; Peter Baker, chief White House correspondent for The Times. For more information on today’s episode, visit nytimes.com/thedaily.