Mamdani won a record-setting primary victory, and unions, grassroots Democratic groups, and savvy elected officials are rushing to back him. Now it’s the establishment’s turn.

First-time voters and young voters turned out in droves for the New York mayoral primary. Their choice for mayor, Zohran Mamdani, may or may not herald a wider tea party-like revolt. But his win serves as a repudiation of the political establishment.