On Tuesday, New York City’s Democratic voters will decide whether Zohran Mamdani controls the future of their party.

With equal parts perfidy and chutzpah, Mamdani has broken with party leaders who supported his rapid rise in last year’s mayoral race to endorse three House candidates.

Three-decade incumbent Nydia Velázquez, esteemed by progressives and Hispanic voters alike, was the first member of Congress to endorse Mamdani last April.

“It’s just beautiful to have someone so authentic,” she gushed in July.

With Velázquez retiring from her NY-7 seat, she thought she could count on Mamdani to repay the favor for her chosen successor, Brooklyn Borough President Antonio Reynoso — a union-backed progressive who isn’t part of the Democratic Socialists of America.

But Mamdani, authentic to himself, failed to follow through.

He’s backing Claire Valdez, a fellow member of the DSA, instead.

Valdez, a 36-year-old transplant from Lubbock, Texas, has only served in the state Assembly since 2025.

Besides organizing a United Auto Workers union at Columbia for clerical workers and her leftist bona fides, she has few qualifications over Reynoso, who has spent decades in New York’s Democratic circles.

But that may not matter if Mamdani’s backing is all it takes to win.

Last year, Mamdani likewise pledged to endorse Rep. Adriano Espaillat, the incumbent in NY-13 covering most of Harlem and part of The Bronx.

The congressman quickly supported Mamdani following his primary win, despite having previously backed Andrew Cuomo.

Instead, Mamdani endorsed Darializa Avila Chevalier, a 31-year-old DSA member and former organizer in his campaign.

Among her many moves that would have been disqualifying not long ago, the radical Chevalier attended a pro-Palestinian DSA rally the day after Hamas’ Oct. 7 massacre and hostage-taking rampage.

No elected officials attended that appalling demonstration, not even then-Assemblyman Mamdani.

Espaillat, in public office since 1997 and chair of the Congressional Hispanic Caucus, has the support of House Minority Leader Hakeem Jeffries, the Congressional Black Caucus and numerous Latino political groups.

Yet he’s having to spend millions to fend off his upstart challenger.

Then there’s Brad Lander, who’s challenging pro-Israel establishment Rep. Dan Goldman in NY-10.

Lander, the former comptroller and mayoral candidate — and a former DSA member — cross-endorsed Mamdani last year, but lost out on a high-ranking role in his administration.

Offloading Lander in a race that has largely become a referendum on Israel both recommitted Mamdani to his anti-Israel base and signaled that even established progressives now rise or fall on his terms.

By any reasonable standard, all these Democrats are firmly on the left.

There isn’t much daylight between them on policies, or on how they’d vote in Congress.

But when it comes to their networks and constituencies, there’s a world of difference.

Mamdani and his allies are betting that a listless Democratic Party will gravitate around the far smaller but ideologically energized DSA, like a planet orbiting a pulsar.

If his endorsees win all three races, no-name radicals across the nation will flock to Mamdani to kiss his ring before launching primary bids.

The DSA-fueled Mamdani machine would become arguably the preeminent force in Democratic politics heading into 2028, even though most of the country doesn’t look like Bushwick.

But if he loses all three, the mayor will have alienated a large swath of the traditional Democratic power structure — especially Hispanic leaders — while exposing the limits of the socialist movement, even in some of the nation’s leftmost congressional districts.

Don’t forget: Mamdani took a hit in April after his dark-horse DSA candidate Lindsay Boylan failed to upset Carl Wilson for Erik Bottcher’s empty City Council seat.

A mixed result would prolong the party’s civil war — though with Mamdani still ahead, given his effort’s underdog nature.

To fully appreciate the mayor’s shrewd political maneuvering, however, look at his approach to crime.

As the mayor backs the hardest-left insurgents for Congress, he’s also standing by his capable law-and-order police commissioner, Jessica Tisch, who has overseen a 6% reduction in serious crime compared to last year.

The NYC DSA chapter recently scolded him on his plans to allow a modest increase in police-officer headcount to implement Tisch’s plans to add a second patrol borough to The Bronx.

Yet Mamdani has held firm against those in his own camp, even defending the NYPD’s choice to deploy officers in riot gear to disperse disorderly Knicks fans after the team’s championship victory.

In other words, he won’t allow the DSA’s anti-police ideology to derail his governing agenda — or his political ambitions.

Make no mistake: Behind the smile and under the Knicks jersey stands a political operator for whom loyalty will always give way to power.

John Ketcham is director of cities and a legal policy fellow at Manhattan Institute. All views expressed are those of the author and not Manhattan Institute.