It’s already clear that the election of Zohran Mamdani as New York City’s mayor is a historic moment — not just for the city but for the Democratic Party and for America’s future on the other side of Donald Trump. Exactly how that history will unfold, and what its long-term consequences will be, are questions we can’t possibly answer here and now. By last Tuesday, Mamdani’s victory was no longer a surprise; he’d held a substantial lead in the polls for months. But it still came as a shock to the system and broke basically all the rules of American...