NEW YORK>> The stunning success of Zohran Mamdani, a 33-year-old self-described democratic socialist, in the race for New York mayor has exposed anew the fiery divisions plaguing the Democratic Party as it struggles to repair its brand nearly half a year into Donald Trump’s presidency.

A fresh round of infighting erupted among Democratic officials, donors and political operatives on Wednesday, a day after Mamdani’s leading opponent, former New York Gov. Andrew Cuomo, conceded the Democratic primary. Mamdani appears on a glide path to the nomination, although ranked choice vote counting will determine the final outcome next week.

Many progressives cheered the emergence of the young and charismatic Mamdani, whose candidacy caught on with viral campaign videos and a focus on the cost of living. But the party’s more pragmatic wing cast the outcome as a serious setback in their quest to broaden Democrats’ appeal and move past the more controversial policies that alienated would-be voters in recent elections.

Indeed, Wednesday’s debate was about much more than who would lead America’s largest city for the next four years.

Giddy Republicans viewed Mamdani’s success as a political gift that would help shape elections across New Jersey and Virginia this fall and into next year’s midterms. And although such predictions are premature, national conservative media focused on the New York election with fresh zeal, suggesting that Mamdani’s emerging profile as a prominent Democratic leader will surely grow.

Trump took aim at Mamdani on social media, calling him “a 100% Communist Lunatic.”

“We’ve had Radical Lefties before, but this is getting a little ridiculous,” the president wrote. “Yes, this is a big moment in the History of our Country.”

Some Democrats think so, too.

Lawrence Summers, the Treasury Secretary under former Democratic President Barack Obama, aired dire concerns on social media.

“I am profoundly alarmed about the future of the (Democratic Party) and the country” because of the New York results, Summers wrote.

Vermont Sen. Bernie Sanders, who had endorsed Mamdani, scoffed at such Democratic critics and instead called for them to follow Mamdani’s lead.

“In many ways, Mamdani’s campaign really shows the direction in which the Democratic Party should be moving. And that is not to worry about what billionaires want but to worry about what working-class people want,” Sanders told The Associated Press.

The Vermont senator warned Republicans against premature celebration.

“People like Mamdani are their worst nightmares,” Sanders said of the GOP. “It’s one thing for the Democrats to be strongly against Donald Trump. It is another thing to give working class people something to vote for — a positive agenda.”

Assuming Mamdani ultimately is the Democratic nominee, he would move to a November election against embattled Mayor Eric Adams, who is running as an independent, Republican candidate Curtis Sliwa and maybe even Cuomo again, should he choose to run as an independent.

A member of the New York Legislature since 2021, Mamdani won over Democratic primary voters with an optimistic message centered on the cost of living backed by a sprawling grassroots campaign that brought out thousands of volunteers across the city’s five boroughs.

Initial precinct data shows that he did well in the city’s wealthier enclaves while Cuomo struggled in all but majority Black and orthodox Jewish neighborhoods, along with the more conservative Staten Island.

Mamdani’s rise was aided by Cuomo’s baggage. The 67-year-old Democrat was trying to mount a political comeback from a sexual harassment scandal that forced him to resign the governorship in 2021.