Supporters of progressive taxation gathered en masse for a “Tax the Rich” rally headlined by Senator Bernie Sanders in The Bronx on Sunday. However, Mayor Mamdani opted not to attend, as he navigates delicate negotiations with Governor Hochul over tax policies.

More than 1,000 attendees packed the expansive performing arts center at Lehman College, where Bernie Sanders (I-Vt.) spent nearly an hour advocating for his plan targeting the affluent.

“A few years back, it was revealed that Elon Musk, the wealthiest individual on the planet, had an effective tax rate under 3.3%, while a typical American truck driver faced an 8.4% effective tax rate,” Sanders declared to the audience, who responded with boos of disapproval and chants of “Shame! Shame!”

“This is the very issue the New York City mayor is championing,” added the 84-year-old senator.

“Across the United States, in New York state, and here in New York City, people are calling for a tax system that is progressive, equitable, and compels the wealthiest to contribute their fair share,” he emphasized.

Sanders has consistently advocated for a 5% federal tax on individuals whose net worth exceeds $1 billion. This mirrors Mayor Mamdani’s push for a 2% additional tax on New Yorkers with annual earnings over $1 million, a proposal he has urged Governor Hochul to endorse since assuming office in January.

Hochul — the only real stumbling block to pass the Mamdani tax — has come right out and said she would not support such legislation, leading to a diplomatic dance between the state’s two most powerful leaders as June budget deadlines and November elections loom.

That dance was put on full display Sunday when Mamdani declined to join his socialist banner-waver Sanders onstage and instead left the lieutenants to make his pitch for him.

“I would ask Gov. Hochul listen to where the people are at,” Sanders said. “The people of this city, the people of this state, the people of this country, do not want to see our kids go hungry. Do not want to see people sleep out on the street lack health care.

“They want the very rich to start paying their fair share of taxes,” he said. “I would hope that the governor joins the vast majority of the people who want to see that happen.”

The past two months have seen periods of tension and detente between Mamdani and the gov.

Hochul in February funneled more than a billion dollars to New York City to help offset a its budget deficit, while Mamdani just days later threatened to hike Big Apple property taxes by nearly 10% if Hochul wouldn’t sign his tax on the wealthy to gain even more revenue.

But Mamdani also endorsed Hochul’s bid for re-election in the fall — and some have speculated she is simply waiting to win her seat back before signing the mayor’s controversial tax into law, as many state lawmakers have voiced support for the measure.

Liberals who turned out to cheer on Sanders on Sunday did their part pushing Mamdani’s agenda on Hochul in his stead.

“I want to say Gov. Hochul — you are the governor because of these people,” 52-year-old Bronx resident Rowshon Sharker told The Post.

“These people voted for you.

“Mamdani trying to do his job, but we are the part of the people,” she said. “We are here to say the words. We elected Mamdani for our basic needs, right, universal child care, housing and every point.”

Leaders from Mamdani’s Democratic Socialists of America also took up the mayor’s cause to take Hochul to task.

“She is a public servant, and she owes us the decency of listening to us,” said city DSA co-Chair Grace Mausser.

“The people of New York have put her there, and the people of New York want to tax and rich. So if she wants to stay in office, she should do it. too.”

Some attendees seemed unfazed by Mamdani’s absence at the rally.

“We have a history of working an inside-outside strategy with all of our electives for years at this point, and we don’t take orders from the mayor,” said Mausser’s DSA co-chair, Gustavo Gordillo.

“We’re here to build an agitational movement that’s going to force the governor to tax the rich, and that’s what the mayor wants as well.

“We want to tell Hochul she needs to choose a side, whether she’s on the side of the working class in New York or on the side of the billionaires and the 1%” he said.