Shortly after midnight on June 25, New York mayoral candidate Zohran Mamdani appeared before his supporters at a rooftop brewery to greet the crowd of supporters chanting his name.

His main rival for the Democratic Party nomination, Andrew Cuomo, had just conceded defeat on television and the mood was delirious. Said Mamdani, quoting Nelson Mandela, “It always seems impossible until it is done.”

Hours later, as the magnitude of his upset became clear, the 33-year-old Mamdani found himself fielding questions about what his victory might mean for the floundering Democratic Party in the United States.

Since losing to Donald Trump in November’s presidential election, the Democratic Party has faced intense criticism from its own supporters who believe their leaders have been too passive in opposing Trump’s agenda and failed to present voters with compelling alternatives.

The party hit historic lows in public approval in April, with merely a quarter of voters holding positive views about the Democrats – the worst showing since tracking began in 1990.

Mamdani’s win has given the party cause to cheer – and perhaps a new roadmap. The result is a “larger referendum about where our party goes”, Mamdani told MSNBC, contending that the Democrats must “move our political instinct from lecturing to listening”.

The victory for Mamdani in Tuesday’s Democratic primary makes him the party’s nominee for New York mayor in November’s general election. A self-avowed democratic socialist, his campaign has advocated policies such as free public transit and rent freezes. He defeated Cuomo – a former state governor with strong establishment backing – despite starting the race with little name recognition.

For the Democratic Party, it may be difficult to seek definitive pointers from the primary election in one city – particularly when that city is overwhelmingly Democratic and the establishment candidate was as flawed as Cuomo, who previously resigned over sexual harassment allegations.

Yet Mamdani’s success provides evidence that the brand of democratic socialism advanced by his wing of the party can attract diverse voters. He received endorsements from Bernie Sanders and Alexandria Ocasio-Cortez, two other prominent politicians who describe themselves as democratic socialists.

Mamdani seems to have been buoyed by the frustration many feel with the old Democratic machine and strategies. His campaign managed to mobilise voters who had previously stayed away from mayoral elections in New York.

Nearly a quarter of early voters were casting ballots in a Democratic primary for the first time since 2012 – a jump from 2021, when only 3% were new to Democratic primaries.

“Mamdani’s focus on concrete economic issues such as free buses, rent freezes, and universal childcare clearly resonated with a wide range of voters,” said Na’ilah Amaru, a policy advocate who works with Democratic politicians. “Campaigns that rely too heavily on past voting patterns miss entire groups of emerging voters who are ready to engage when offered something real.”

Mamdani’s campaign released a statement to journalists on Thursday that he had won working-class neighborhoods that Mayor Eric Adams had carried in 2021, and captured areas that swung toward Trump in 2024.

The campaign’s scale was also unprecedented for a municipal race, deploying over 50,000 volunteers who knocked on 1.5 million doors –in a city with 4.7 million Democrat voters and a population of 8 million.

Mamdani also benefitted from New York City’s public financing system, which is designed to level the playing field and reduce the influence of wealthy donors. Under this system, for every dollar up to $250 that a city resident contributes to a campaign, the city government adds another $8 from public funds.

In March, Mamdani became the first candidate in the election to reach the $8 million spending cap for the primary. He did so with donations from a far more diverse sources than Cuomo: while Cuomo’s campaign had 5,730 donors giving an average of $700 each, Mamdani was backed by 20,720 donors averaging $82.

Another source of disappointment among the Democratic base that Mamdani tapped into was the party’s messaging around the violence in Palestine. Many voters have criticised Democratic leaders, including presidential candidate Kamala Harris, for remaining largely silent as tens of thousands of Palestinians were killed.

Mamdani is a rare US politician who has openly declared his support for Palestine, even as he runs to be mayor of a city in which estimated 11.6% of the population is Jewish.

Raza G, who worked with a South Asian collective canvassing voters for Mamdani’s campaign, contended that the results demonstrated “a breakdown of the centre” in Democratic party politics.

“The election was between a candidate who was pro-Palestine and another who was backed by pro-Israel groups,” he said. “Voters saw that in the silence of Kamala Harris, the Democratic Party did not have a plan to address the question of Palestine and at the same time saw in Mamdani someone who has consistently spoken up about Palestinian rights.’

Raza added that unlike Harris, Mamdani did not disengage from voters who disagreed with him. “People may have moved to the right but Mamdani understood that these people wanted an end to the violence and wanted inflation to reduce,” he said.

While Mamdani worked to mobilise the South Asian and Muslim communities that had a historically low turnout in mayoral elections, his campaign also made an effort to engage with Jewish voters.

Daniel Aldana Cohen, an assistant professor of sociology at UC Berkeley, suggested that Mamdani’s campaign could be used across the US.

“When Mamdani talks about the cost of living, he’s talking about solutions,” Cohen said. “He’s emphasising tangible benefits for ordinary people while keeping economic issues front and centre – but not at the exclusion of everything else like opposing bigotry…This is certainly a national model.”