Zohran Mamdani will be the unlikeliest mayor in New York City history. A 34-year-old backbench state assemblyman and self-proclaimed democratic socialist, Mamdani ran on the promise of affordability and was declared the winner not long after polls closed tonight. On his path to victory, he thrilled young voters in a way that few Democrats have in years. But perhaps no one was more delighted by his election than President Donald Trump. Mamdani’s victory was his second decisive win over former Governor Andrew Cuomo, whom he defeated in the Democratic primary in June. (The current mayor, Eric Adams, skipped the primary,...