Roasts are not usually vehicles for deep introspection, but during his remarks at this year’s Al Smith dinner on Oct. 17, Donald Trump’s lips issued something that sounded suspiciously like an apology. It concerned his own joke that he judged had gone too far, about Democratic opponent Kamala Harris’s child care plan. “The only piece of advice I would have for her in the event that she wins would be not to let her husband Doug anywhere near the nannies,” Trump told the crowd at the $5,000-a-plate Catholic charities fundraiser at New York City’s Waldorf Astoria Hotel. “Just keep them away.” The joke concerned would-be first husband Doug Emhoff, whose union with Harris is his second marriage after his first marriage ended in divorce. One cause of the split was Emhoff’s reported infidelity with the...