In August Mr Duncan joined a chorus of Republican politicians campaigning against Mr Trump when he endorsed Kamala Harris on stage at the Democratic National Convention. “It was like the first day getting traded from the Yankees to the Red Sox,” he says of sitting in the green room waiting for his debut. Since then Liz Cheney, once the third-most powerful Republican in the House, and her father, former vice-president Dick Cheney, have said that they, too, will vote for Ms Harris.