“Tonight was not our night. I called him, I congratulated him. He won,” Cuomo, a political veteran who was struggling to recover from a sexual harassment scandal, told his supporters at an election night party.

In what appears to be a rebuke by the left-leaning city to moderate veterans of the Democratic Party — and to the rarely acknowledged native Republican, US President Donald Trump — Mamdani leads with 43% of the vote with 95% of ballots counted, city officials said.

Nearly a dozen candidates ran in the party's primary election for mayor of the largest city in the US, where registered Democrats outnumber Republicans by three to one, AFP reported.

Voters cast their ballots in sweltering heat before polls closed at 9 p.m., but results could take time to finalize.

The election is based on a preferential voting system. Voters must select five candidates in order of preference, and neither Cuomo nor Mamdani received the necessary majority.

If no candidate wins 50% of the vote, election officials begin eliminating the lowest-ranking candidates and recounting the votes, which could take days.

With Democrats across the country still reeling from Trump's presidential election victory last year, the high-profile race in the city did little to calm party nerves.

But Mamdani's optimistic campaign, built on youthful social media skills and promises to improve the city's accessibility, appears to have resonated with voters.

Cuomo resigned as governor of New York four years ago after several women accused him of sexual harassment. He was also accused of mismanaging the state's response to the COVID-19 pandemic.

A staunch supporter of Israel, Cuomo led in the polls for most of the campaign, thanks to his widespread name recognition as the son of another New York governor, as well as support from influential centrist figures, including former President Bill Clinton.

Mamdani, on the other hand, is backed by the Democratic Socialists of America, a niche left-wing organization that could work in the Big Apple but which many analysts warn against.

The fact that Mamdani is an advocate for the Palestinians and has accused Israel of “genocide” also makes him a prime target for Trump.

Among his supporters are two of Trump's favorite opponents — the fiery leftist Senator Bernie Sanders and the progressive Congresswoman Alexandria Ocasio-Cortez, both of whom congratulated Mamdani.

“Billionaires and lobbyists poured millions against you and our public financing system. And you won,” Ocasio-Cortez wrote on Twitter.

“You stood up to the political, economic, and media elite — and you defeated them,” Sanders wrote. | BGNES