NEW YORK — Zohran Mamdani, a 33-year-old democratic socialist lawmaker, is on pace to win the Democratic primary for New York City mayor — a seismic shift in what normally would have been a sleepy reelection for the incumbent, Eric Adams, and one that involved toppling Andrew Cuomo’s political comeback.

Cuomo conceded defeat late Tuesday night and said he called to congratulate Mamdani.

“Tonight was not our night” Cuomo said at the headquarters of the New York City carpenters union. “I’m very proud of the campaign that we ran.”

Mamdani won 43.5 percent of first-place votes to Cuomo’s 36.3 percent, according to the New York City Board of Elections. But that outcome is not final. The board is expected to announce full results on July 1 in an election that utilized ranked choice voting, which allows New Yorkers to pick up to five candidates in order of preference.

Unlike Cuomo, Mamdani employed a ranked choice strategy by cross-endorsing third-place finisher Brad Lander, so he stands to benefit from the practice. But polling in the race was tight, and Cuomo led nearly every public opinion survey, bolstered by a $25 million super PAC that flooded airwaves and mailboxes with anti-Mamdani and pro-Cuomo messaging.

If Mamdani’s lead holds, it would mark a humiliating defeat for Cuomo, a fixture in New York politics who tried to resurrect his career four years after resigning in disgrace, following sexual harassment and Covid mismanagement allegations. A Mamdani victory would also be tantamount to a political earthquake that will reverberate across the country, as the Democratic Party — still reeling from its losses last year — tries to chart its path forward. His lead late Tuesday night portends what will likely be an historic triumph of the party’s left wing in the biggest city in the United States, for one of the highest-profile jobs in American politics.

The hard-fought local fight mirrors the national Democratic divide: A young, inexperienced socialist running on a hopeful message with the backing of Bernie Sanders and Alexandria Ocasio-Cortez versus a 67-year-old, three-term former New York governor who worked in Bill Clinton’s Cabinet and got the ex-president’s endorsement in the race’s waning days.

It is also the most high-profile Democratic primary in the country since President Donald Trump won a second term seven months ago. Seen as a referendum on how Democrats should counter the White House, New Yorkers lined up in droves during nine days of early voting, many of them matching the profile of a prototypical Mamdani supporter: Young, white and in gentrifying areas of the city. If the results Tuesday night hold, they will have chosen a new voice focused on affordability over a party elder who leaned into his prior experience fighting Trump and promised to restore order to Adams’ chaotic City Hall.

Buoyed by that relentless focus on affordability — Mamdani pledged to freeze the rent on more than a million regulated apartments and push for a tax increase on the rich to fund free buses and create city-owned grocery stores — the social media savvy state lawmaker earned a devoted following that included more than 50,000 volunteers. That workforce is unprecedented in a New York City race, according to Jerry Skurnik, a longtime political consultant.

The election also reflects a reshaped electorate: More than 980,782 Democrats voted in the mayoral primary, an increase over the 942,031 who turned out in 2021, and the most since 1989, when more than 1 million New Yorkers turned out to nominate the city’s first Black mayor, David Dinkins. And, as The New York Times recently reported, the Black population may be eroding in New York City.

“We were never assuming that we would sneak into this nomination in a low turnout environment,” Mamdani spokesperson Andrew Epstein said Tuesday night. “We wanted people turning out in record numbers.”

Modern history dictates that Democratic nominees typically win in New York City races, but Mamdani faces a complicated, crowded and challenging general election.

Adams is seeking reelection on an independent line after opting out of the Democratic primary — a decision prompted by low approval ratings after he embraced Trump, whose administration moved to dismiss federal corruption charges against him. Republican mainstay Curtis Sliwa is running again, after securing 28 percent of the vote in 2021. Well-funded independent Jim Walden will be on the ballot too. And Cuomo has secured an independent line in the general as well.

“I’m on the general election ballot,” Cuomo said while casting his vote Tuesday morning.

Either way, Mamdani is likely to face fierce opposition, backed by millions of dollars. A super PAC supporting Cuomo relentlessly attacked Mamdani for his inexperience, his criticism of Israel and his alignment with pro-Palestinian campus activism.

“This is a capitalist city that has a historic relationship with Israel,” said Kathy Wylde, who lobbies for the city’s big business interests as the president of the Partnership for New York City. “Should he win the primary, he’s going to have to deal with that. Or there will be a serious surge to try and prevent him from becoming mayor.”

Mamdani was barely known citywide when he launched his campaign in October, having served fewer than five years in the state Assembly and accomplishing very little, legislatively, during that time.

His possible success next week would mark a stunning fall for Cuomo, who had money, a dynastic family name and the begrudging backing of the Democratic establishment — all at the hands of a socialist half his age, with an openly hostile attitude toward Israel in a city of nearly 1 million Jews.

After launching his campaign in March, Cuomo dodged media appearances and candidate forums. He ran a largely nostalgia-based campaign focused on his nationally recognized televised briefings during Covid as governor and wins like legalizing same sex marriage and rebuilding LaGuardia Airport after then-Vice President Joe Biden derided it as one you’d find “in a third world country.”

He painted a doom-and-gloom portrait of the city in his unusually long 17-minute launch video and spent as much time attacking his cheery rival as he did trying to instill hope in New Yorkers, who repeatedly demanded the city go in a different direction. Cuomo leaned into his strengths — experience, management, tough talk on Trump — but focused less than Mamdani on affordability, which generally ranks as voters’ top concern.

The ex-governor’s record came with baggage too. He resigned under pressure in 2021 after an attorney general’s report found he sexually harassed 11 women, which he denies. Cuomo was also accused of covering up deaths from Covid in nursing homes, and is now reportedly under investigation by the Trump administration for lying in Congressional testimony last year — a charge he also denies and derides as politically motivated. Opponents say Cuomo caused many of the problems he now wants to fix — by mismanaging the transit system, reducing public employees’ benefits and cutting homeless services funding.

He entered the race a heavy favorite, and he led every poll for months. But while his support remained more or less steady, Mamdani gained. An Emerson College poll released the day before the election showed Cuomo winning the most votes in the first round, but Mamdani coming from behind when ranked votes were factored in to win overall.

Elections worldwide in recent years have shown voters fed up with the establishment, and in New York City, no one embodies that more than Cuomo, who’s father Mario served as governor from 1983 through 1994.

Born in 1991, Mamdani would be the youngest mayor in more than a century. A Muslim of Indian heritage who was born in Uganda and immigrated to New York at 7 years old, a Mamdani mayoralty would mark many firsts for New York City.

Led by Cuomo, critics called Mamdani’s plans to expand city-funded services a fantasy, as they would rely upon a tax increase the governor is unlikely to grant, and slammed him for a lack of experience. He was elected to the Assembly in 2020, where he’s managed a staff of five. If he wins, the politics of New York City and managing a public workforce of 300,000 will present an enormous challenge.

Mamdani has pointed to his campaign as the answer. If he succeeds next week, it will be over the objections of most of the city’s unions, local party leaders, editorial boards and the real estate and financial executives.

“To everyone who pulls me aside to whisper with the best intentions: ‘You have already won,’ Mamdani said at a campaign rally earlier this month, joined by Ocasio-Cortez. “I am sorry, but the days of moral victories are over. This campaign is going to win on June 24 — and it’s thanks to each of you.”