One afternoon in late September, passersby gawked as Zohran Mamdani stepped out of a black SUV in Midtown Manhattan and strode to a small lectern his team had set up on the sidewalk. A gaggle of reporters, photographers and TV cameramen was waiting, their sight lines clear, on the stretch just south of Central Park known as Billionaires’ Row, a line of ultraluxury apartment buildings so tall they cast shadows over the park. Mamdani was standing in front of one with an $87.5 million listing inside: a four-bed, seven-bath excuse to talk about the cost of living in America’s priciest city. “This is a part of New York City that can boast the cost of an apartment exceeding $200 million,” he said, a world apart from the material concerns of most residents, “whether they can afford their rent, their child care, their groceries.”