This extreme descriptor is rooted in Mr Mamdani’s progressive platform that mainstream Democrats eschew: Free bus rides and child care, and the imposition of a four-year freeze on rents in rent-controlled apartments to address the cost-of-living crisis. Funding for these freebies is to come from a sharp increase in corporate-tax rates from 7.25 to 11.5 per cent and a 2 per cent tax on incomes above $1 million, explaining why billionaires bankrolled his opponent. Though the less wealthy districts — the Bronx, Brooklyn, and Harlem — delivered the expected votes, Mr Mamdani scored surprise victories in some upscale neighbourhoods such as the Upper West Side and parts of the Village. Still, this charismatic former New York state representative will have his work cut out meeting these heightened expectations. First, his funding plans need to be approved by a state legislature dominated by mainstream Democrats. Second, in an era of increasingly mobile capital, his tax plans could precipitate a flight of businesses to lower-tax jurisdictions, which could restrict the city’s growth on which he is banking to deliver more revenue.