“We did not have a lot of money,” said JD Vance, placing hand on heart as he recalled his childhood in Middletown, Ohio in the 1990s. “I was raised by a woman who struggled often to put food on the table and clothes on her back.” There was an earnest cry from the audience. “Mamaw!” shouted a man. Smiling at the reference to his grandmother, the US vice-president said: “Everybody loves Mamaw. Most of all me.” But there was also a political point to the story: despite the hardships, Vance insisted, Mamaw never had to worry about violent crime until...