In a huge win for the Democrats, Zohran Mamdani has been elected mayor of New York City. He ran on an explicitly leftist platform, focused on affordability and the working class — but many of his own party's top leaders have been reluctant to endorse him. Some still haven't.

A rift is growing between the party's centrist establishment, keen on partisan opposition to Trump and appeasing wealthy donors, and the progressive wing of the party newly energized by Mamdani, who promises to tax the rich and fight what he sees as a growing oligarchy.

Joshua A. Cohen is the author of the American politics newsletter Ettingermentum. He breaks down the battle for the soul of the Democratic Party.