After several bruising weeks for Speaker Mike Johnson, a soft-focus podcast interview alongside his wife, conducted by Katie Miller, the wife of Stephen Miller, one of President Trump’s top advisers, had all the ingredients for a flattering reset. What emerged from the interview instead was a portrait of a Republican leader barely keeping his head above water in a job to which he does not appear particularly well suited, a conversation full of tragically revealing details packaged as rueful humor but with the biting sting of truth. “We have this joke that I’m not really a speaker of the House,”...