For a while, McCain and Salter planned to call their final book “It’s Always Darkest Before It’s Completely Black.” But McCain pulled back—it was too much. “McCain never abandons all hope,” Salter said. “It’s not the country. It’s just this jackass.” I asked what, for McCain, had been the worst moment of Trump’s ascendance. “The Khans,” Salter said. In the summer of 2016, when Trump began attacking Khizr and Ghazala Khan, whose son was killed while serving in Iraq, Salter was driving from New Hampshire, where he had been consulting on Ken Burns’s Vietnam War documentary, to Maine. McCain called. “He was distraught,” Salter said. “He said, ‘Did you see that asshole?’ ” Salter went on, “I knew then that he would never go the distance. That he would formally say, ‘I can’t vote for him.’ ”

McCain went to Iraq and Afghanistan scores of times, but the event that stuck with him most, Salter said, was a reënlistment and naturalization ceremony that David Petraeus held in Iraq on the Fourth of July, in 2007, for soldiers who had yet to become citizens. “And there were two pairs of boots on two chairs,” Salter said. “Two guys who were about to become citizens but they were killed that week. And he’s told me that story a hundred times and he cries every time he tells that story. Petraeus had some line—‘They died for their country before it was their country.’ It was like a gut punch to him. That’s who the Khans’ son was to him.”