Senator Mitt Romney, former Republican presidential nominee, has announced his retirement at the end of his current term, but he is not going quietly. On his way out he is making his feelings about past and current colleagues abundantly clear, with particular scorn directed at Donald Trump and his acolytes for what they’ve done to the Republican Party and the country broadly. McKay Coppins, author of the newly published “Romney: A Reckoning,” talks with Alex Wagner about his interactions with Romney in the course of writing the book.