Lefty wunderkind Morris Katz allegedly stiffed his Brooklyn landlord for months — racking up  $14,000 in unpaid rent — and left the Williamsburg pad stuffed with trash when his lease was up, The Post has learned.

Katz — the 27-year-old nepo baby credited with fueling socialist Mayor Zohran Mamdani’s meteoric rise — missed multiple rent payments and bounced checks during his six-month lease of the top-floor duplex on Lorimer Street, according to two sources with knowledge of the dilemma. 

“I don’t get him. He don’t have his priorities in order, that’s for sure,” super Felix Barbosa told The Post while hosing down the sidewalk outside the four-story building Thursday.

Morris Katz has been one of Mamdani’s top political advisors. Morris Katz Felix Barbosa, the building’s super, complained to The Post about the unpaid bills and mess Katz left. Stephen Yang for NY Post

“When you come from a rich family, you don’t have your priorities in order,” he said. “He’s not a bad guy, but his priorities are all f–ked up.”

Barbosa also alleged: “He owes Con Edison money. He owes the gas company money. He owes everyone money.”

Katz signed the short-term lease in November, agreeing to pony up $6,500-per-month for a two-bed, three-bath apartment with a private roof deck, according to documents reviewed by The Post.

But the in-demand far-left political strategist was late on his rent for the first three months, forcing the building reps to hound him down for the payments, one source said.

Katz left the apartment a mess for weeks after his lease was up. Obtained by NY Post

Eventually, Katz allegedly stopped paying entirely, according to the source.

At the time, the co-founder of lefty consulting group The Fight Agency was coming off a big-time win after playing a key role in propelling Mamdani — a formerly relatively unknown, backbench state lawmaker — into City Hall.

He was also offering his advice to a number of congressional candidates running in New York’s June Democratic primaries, including Democratic Socialists of America firebrands Darializa Avila Chevalier and Claire Valdez, as well as Brad Lander and Micah Lasher. 

Katz conceded that he emptied out the apartment once returning from a work trip. Obtained by NY Post

The young operative had also taken on advising former Maine Senate hopeful Graham Platner, whose campaign later imploded when he faced a rape accusation, leaving Katz embroiled in controversy after he allegedly threatened a whistleblowing ex-staffer.

It wasn’t until he was set to move out on April 30 that Katz offered up the full payment of back rent, after initially bouncing a check, the sources said.

“It was one of those things to get the rent you had to pull out his f–king teeth,” Barbosa said. “But then he came back and paid everything, $14,000. I don’t know where the money came from.”

Trash and furniture were left behind. Obtained by NY Post

Katz, though, left the place in shambles for weeks after he was supposed to clear out, according to photos obtained by The Post.

The snaps show a loaded bar cart, junk-filled closet, random furniture and a fridge packed with takeout boxes and wrapped-up leftovers.

“He has too much on his plate that he can’t handle, that’s what happened with him. He didn’t clean up the place at all. He didn’t clean up any of his s–t,” the super said.

The apartment wasn’t cleaned out until early June, according to the sources.

A stocked bar cart was also abandoned. Obtained by NY Post

Katz, reached by The Post on Thursday, tried to claim that the super’s comments were being taken out of context — but did not dispute any of the claims, only saying he stayed in “communication” with the landlord during the months he wasn’t paying rent.

He blamed a snafu involving a new bank — and said he eventually got his relatives to help make good on the rent.

“When it came time to settle the balance, Morris didn’t yet have a checkbook with his new bank, so he sent his family the funds to use theirs and paid the balance in full,” a Fight Agency spokesperson said in a statement on his behalf.

Bedding and pillows on the floor of the apartment.. Obtained by NY Post

“When he returned from traveling for work, he cleared out his remaining belongings.”

The progressive rising star, who was the subject of glowing magazine and newspaper profiles, grew up in a $5 million apartment with his famous screenwriter and TV producer pops, David Bar Katz, and mother Julie Merberg, who is a children’s book author.

His parents’ careers gave him the opportunity to rub elbows with big-time actors, and most notably, his godfather was the late Philip Seymour Hoffman.

The privileged upbringing was similar to his pal Mamdani, who grew up in the Upper West Side and whose mom is an award-winning filmmaker and dad is a renowned academic who teaches at Columbia University. 

The rent dodge is just the latest instance of folks in the mayor’s orbit brushing off landlords. 

A key initiative of City Hall — led by tenant advocate Cea Weaver, who has called for the seizing of private property — has been to target landlords whom the administration believes are bad actors.

The Mayor’s Office of Mass Engagement has also prioritized getting tenants to turnout to board meetings to champion the admin’s rent-freeze on stabilized units.