“I am a democratic socialist.” These words were really spoken by an American politician on live TV, just hours after being elected to govern a city with a population greater than that of all but twelve US states, in the year 2025. In the big, packed room in Brooklyn where I watched Zohran Mamdani’s victory speech, every other sentence brought cheers of joy. But after those five words the roar was like a waterfall, a dam breaking. Several spirits presided over Mamdani’s remarks, which he gave to an ecstatic crowd at the Brooklyn Paramount, a newly refurbished deco movie palace turned concert hall in the borough’s downtown. The first was Eugene V. Debs. “I can see the dawn of a better day for humanity,” Debs told a starkly different audience on September 18, 1918. That day, the Socialist Party leader addressed the judge in an Ohio courtroom, where he had just been convicted under the new Espionage Act for a different speech, which Debs had given three months earlier.…