Zohran Mamdani, once championed by Bill de Blasio, is now facing criticism from his former supporter, who claims the policies Mamdani is promoting are financially unsustainable.

Although de Blasio has been backing the Democratic candidate, even wearing a “Hot Girls for Zohran” shirt at a recent demonstration, he expressed skepticism about Mamdani’s $10 billion plan of socialist initiatives during an interview released Tuesday.

“From my perspective, the numbers don’t withstand scrutiny, and the political challenges are considerable,” de Blasio mentioned to The Times of London, after apparently taking a closer look at the intricacies of Mamdani’s ambitious proposals, which include free public transportation and universal childcare.

“Though the aspirations are commendable, the projected costs — reportedly surpassing $7 billion annually — are based on optimistic assumptions about eliminating inefficiencies and generating new tax revenues,” de Blasio explained to the publication.

To finance his extensive agenda, Mamdani suggests cutting billions from existing budgets and imposing higher taxes on the affluent and corporations.

The DSA hopeful recently praised de Blasio as his favorite, recent New York City mayor.

It was unclear how de Blasio seemingly just realized what Mamdani had been putting out after penning a fawning op-ed about the Queens assemblyman in September — claiming his “bold, sweeping” agenda would save the city.

“We don’t just need Zohran Mamdani to be our mayor because he has the right ideas, or because they can be achieved,” de Blasio wrote in the op-ed.

De Blasio has long been an ally of Mayor Eric Adams and even gave him a heads-up that the op-ed was coming, telling the sitting mayor he would have been in his corner if stuck with the Democratic Party line.

Adams just recently backed ex-Gov. Andrew Cuomo’s independent bid for mayor and was out on the campaign trail stumping for him on Tuesday.

Calls to de Blasio were not returned.