The first is Elizabeth Simons, the daughter of the late hedge fund billionaire Jim Simons (d. 2024) who shares a $32.5 billion fortune with her stepmother Marilyn and two siblings. She cut a check for $250,000 to New Yorkers For Lower Costs, the main independent group backing Mamdani’s campaign, in August.

GitHub cofounder Tom Preston-Werner, 45, is Mamdani’s other billionaire backer; in April, he sent New Yorkers For Lower Costs a check for $20,000. Preston-Werner, also a Bay Area resident, started the software development platform in 2008 and became a billionaire after Microsoft bought the company for $7.5 billion in 2018; his net worth is about $1 billion today, Forbes estimates. He now runs a venture capital firm called Preston-Werner Ventures.