David Dinkins shaking hands with members of the community alongside Jesse Jackson in Queens in 1989. Mr. Dinkins himself was, at some point, a card-carrying member of the Democratic Socialists of America.

In the fall of 1990, Mayor David Dinkins was watching homicides surge and his popularity plummet — “Dave, Do Something,” implored The New York Post — when he found himself in a room that was much more comfortable, more matched up with the lefty ideals that had sent him into politics in the first place.

Under a banner of the fist and rose, facing union bigwigs and foreign left-wing leaders, the mayor of New York gave a speech not about the crises of the city, but about the promises of socialism.

“Socialist ideals have played a powerful role in this city,” Mr. Dinkins, dressed in a sharp suit and striped tie, told a council meeting of the Socialist International in October 1990. “Public education, a strong and vibrant trade union movement and many great cultural institutions are products of the socialist movement.”

Historically, he’s right: Throughout the history of New York, a city of immigrants and political machines and union loyalists, democratic socialist voices have been part of the thrum of local politics. Mr. Dinkins himself was, at some point, a card-carrying member of the Democratic Socialists of America.

Yet as Zohran Mam