Zohran Mamdani's biggest threat is not Donald Trump, it's the Democratic old guard | Emma Brockes

The New York mayor-elect sells a political message further to the left than any American politician has dared to in recent memory

The morning after Zohran Mamdani's startling mayoral victory in New York, the most arresting visual image was not of the mayor-elect celebrating in an applause-filled room, but the breakdown of voting patterns across the city. Street by street, practically building by building, you could index New Yorkers' support for Mamdani or Andrew Cuomo to the probable amount of rent they were paying. A middle-income precinct on the Upper West Side, for example, showed up as a small island of Mamdani voters in a sea of Cuomo-voting wealthier neighbourhoods. Solid lower-income support for Mamdani in modest midtown gave way to the incredible banking wealth of Tribeca and its majority support of Cuomo.

Allowing for large anomalies - Staten Island, a middle- to lower-income part of the city, voted heavily for Cuomo, as did lower-income Hassidic neighbourhoods in Brooklyn and Queens - the message of the huge turnout for Mamdani in the US's most expensive city seemed to be one of affordability; even of a referendum on capitalism as we know it. And so the most pressing question became: was it a crank result from an unrepresentative city, or the beginning of a new political wave?