The morning after Zohran Mamdani’s surprise victory in the New York City Democratic mayoral primary, Tom O’Donoghue’s phone was ringing off the hook. O’Donoghue, who runs a luxury construction firm in the Hamptons — the summer playground for rich New Yorkers — said his clients were in “complete disbelief” that a socialist was suddenly the favourite to win November’s general election. “One of my clients has 150 commercial buildings in the city and he just told me that he had contacted his attorney this morning. They’re getting out of New York,” he said. Though the former New York governor Andrew...