Zohran Mamdani’s monumental victory in the New York City mayoral primary over former governor Andrew Cuomo was a rare bright spot for a beleaguered US left. But the fight is just beginning for Mamdani and his allies. Should he win the general election next month, a Mamdani administration is almost certain to face fierce attacks from business elites and political opponents inside and outside the Democratic Party.

Mamdani’s primary win, powered in no small part by the New York City chapter of Democratic Socialists of America (NYC-DSA) and aided by support from the labor movement, shows that left-wing politicians can find strength in mass membership organizations. A potential Mamdani administration will need the city’s unions and left-wing organizations to bolster his political capital and apply pressure on the city council and the state legislature to pass his ambitious agenda. Preemptive planning and cooperation between Mamdani and unions and left organizations like DSA can help make his mayoralty a success.

Skepticism over whether Mamdani will deliver on his promises is warranted, especially after seeing the serious headwinds often faced by progressive mayors. Some commentators have compared Mamdani to Chicago mayor Brandon Johnson because of their similar policy priorities, and Johnson’s mayoral tenure offers some potential lessons. There have been wins during Johnson’s tenure as mayor, such as the abolition of Chicago’s subminimum wage for tipped workers; with those victories came some missteps, such as a failure to effectively communicate with the public. Some of Johnson’s most progressive accomplishments as mayor were the result of outside agitation from grassroots organizations.