"[Zohran Mamdani] has…put together a coalition of working-class New Yorkers," Alexandria Ocasio-Cortez said when she endorsed him. It’s a vivid story, but is it true? Tuesday’s exit polling tells a more complicated one. The decisive bloc that gave Mamdani a resounding victory wasn’t the very poorest New Yorkers or the ultra-rich; it was the middle and upper-middle. In New York City—where the average household income is about $128,000—that’s less of a paradox than it sounds. But claims from both sides that the young socialist rode a wave of working-class anger are wide of the mark...