Mamdani’s victory over the 67-year-old Cuomo marked a significant win for the progressive wing of the party over its establishment candidate. Cuomo, who stepped down as governor in 2021 amid sexual harassment allegations, had been heavily favoured entering the primary race.

“Tonight we made history,” Mamdani said in a victory speech to supporters. New Yorkers “have stood up for a city they can afford.”

Cuomo spoke to a sombre crowd at a union hall on Manhattan’s West Side.

“Tonight was not our night,” he said. “I want to applaud the assemblyman for a really smart and good and impactful campaign. Tonight is his night. He deserved it. He won.”

The victory sets up a general election contest between Mamdani and Republican nominee Curtis Sliwa, though Cuomo may choose to run as an independent candidate. Incumbent Mayor Eric Adams will also mount an independent challenge.

The voting on Tuesday took place in sweltering heat — the city recorded a record-breaking 39°C — with overall turnout on the verge of 1 million votes, Bloomberg reported.

Cuomo has been a political force since the 1990s while the 33-year old Mamdani entered the political fray only in 2020 when he was elected to the New York State Assembly.

Faced with stiff odds, Mamdani’s campaign focused on appealing to the everyday concerns of New Yorkers. He backed rent freezes, free bus services and establishing government-run grocery stores to help people with the rising prices of essentials. Essential to Mamdani’s success was a slick social media campaign that featured him walking the streets of New York, engaging voters directly and even echoing Bollywood movies to win support.

That allowed Mamdani’s campaign to swiftly close the gap with Cuomo and even pull ahead in some polls.

But, Mamdani also faced tough questions about his past progressive positions, including his support for “defunding the police” which was seen as a serious liability. His criticism of Israel’s government for its policy in Gaza also attracted scrutiny in a city where Jewish voters are an active political force. In general, Mamdani’s opponents characterised him as too young, too inexperienced and too radical to govern America’s most populous city.

Mamdani’s victory carries significance beyond New York politics for two reasons. One, he placed his identity as a Muslim immigrant at the center of his campaign during a period of intensified national debates over religion, identity and immigration under President Donald Trump.

Two, his upset raises questions about the Democratic Party’s direction as it prepares for 2026 midterm elections. Cuomo’s defeat by a more radical candidate could signal a resurgence of the party’s progressive wing and potential internal conflicts, which could leave the party in factions as it grapples with how best to tackle the political challenge posed by Trump.

If elected mayor, Mamdani would join the highest ranks of Indian-origin politicians in America.

Both of Mamdani’s parents are of Indian descent. His mother is the renowned Indian-American filmmaker Mira Nair, and father the noted Indian-Ugandan postcolonial studies scholar at Columbia University Mahmood Mamdani. Mahmood Mamdani was born in Mumbai and Mira Nair in Rourkela, Odisha.

The broader political rise of Indian-Americans began with Bobby Jindal’s 2004 election to the US House of Representatives, the first Indian-American congressman in half a century.

In the two decades since, Indian-origin politicians like Nikki Haley, Kamala Harris and Ro Khanna have risen to prominent national roles.

Indian-Americans - and the South Asian diaspora more broadly - were a key target demographic for Mamdani’s campaign. According to the Pew Research Centre, roughly 710,000 Indians live in the New York metropolitan area.

Mamdani conducted outreach in regional languages, critiquing income inequality in Hindi and explaining the election’s ranked-choice voting system in Bengali. His campaign hosted “Chai with Zohran” sessions to connect with voters.

However, his comments on Indian Prime Minister Narendra Modi have generated controversy. During a campaign event in May, Mamdani criticised Modi over the 2002 Gujarat riots.