Well, that didn’t take long.

A day after describing himself as a “fiscal conservative,” Bill de Blasio reversed course Saturday — casting himself as a progressive.

“I’ll try this on for size: I am a fiscally responsible progressive,” de Blasio declared.

The Democratic front-runner’s about-face came while he and Republican rival Joe Lhota both attended a Harlem birthday bash for the Rev. Al Sharpton, who turned 59 on Thursday.

When a reporter asked de Blasio to elaborate on his record of fiscal conservatism, de Blasio refused to provide examples.

“If you look at the whole quote, I tried to get it right and say I am a progressive, I am an activist, I’m also fiscally cautious,” he said, referring to his comment a day earlier to a roomful of influential business leaders at the Marriott Marquis.

Lhota laughed off both of his opponent’s claims and attacked de Blasio for equating fiscal conservatism with balancing the budget.

“That’s not fiscal conservatism; it’s following the law,” Lhota said. “Complying with the law is neither conservative nor progressive. It’s compliance. Plain and simple.”

Additional reporting by Jennifer Bain