His potential victory could bring what the Street despises the most — tax hikes and tighter regulation that threaten corporate and investment interests.

Sen. Chuck Schumer and Rep. Hakeem Jeffries, New York City natives who lead their parties’ caucuses in each chamber of Congress, quickly issued statements saying they had spoken to Mamdani and praising the campaign he ran. They stopped short of endorsing him.

Zohran Mamdani's dramatic, strong showing in New York City’s Democratic mayoral primary is putting the rest of the Democratic Party on notice.