With Zohran Mamdani emerging as the clear frontrunner to be the next mayor of New York, American conservatives have another Left-wing, Muslim, big city mayor in their sights: Sir Sadiq Khan. They see a warning from across the Atlantic, where they say progressive policies have accelerated crime rates and economic challenges in London. Then there is religion. “And we must ask ourselves the question and we have the courage to do this on our show,” as Charlie Kirk, the conservative campaigner put it on his podcast three months before being shot dead, “are you comfortable with both London and New...