Democratic mayoral contender Sal Albanese joked Thursday that Mayor de Blasio drop his allegiance to the Boston Red Sox and slammed both hizzoner and the Sox for their cheating ways.

A day after squaring off with de Blasio in the second and last debate before Tuesday’s primary, Albanese declared on the steps of City Hall that he would now describe the mayor as “Boston Bill” — a reference to several of his lies.

“There must be something in the water in Massachusetts. Between the New England Patriots and the Boston Red Sox, they can’t seem to tell the truth,” Albanese said, referring to both teams’ cheating scandals.

“Bill de Blasio — obviously from Boston — from now on shall be known as Boston Bill because he lies repeatedly.”

On a more serious note, Albanese, a Yankees fan who tried out for the team in 1968, attacked de Blasio for not providing a full list of donors who didn’t get favors from City Hall — as promised — and for not footing the bill for the legal fees from several probes into de Blasio’s fundraising efforts.

Taxpayers are now shouldering the burden after de Blasio vowed they wouldn’t get stuck with it.

Every time I go to the Bronx, I point out that Bill de Blasio is a bum because he roots for the Red Sox,” Albanese. “We’ve got two great baseball teams here. He should say I’m going to be rooting for my home teams now.”

Albanese, who said he tried out for the Bombers as a second baseman at the old Stadium, conceded though that Hizzoner doesn’t have “to speak negatively about the Red Sox” and “could still root for Boston if they’re not playing the Yankees or the Mets.”

The de Blasio campaign dismissed the sports analogy.

“Mayor de Blasio expanded Pre-K for every 4 year-old and will do the same for every 3 year-old. Crime is at record lows, jobs are at a record high, New York City is building affordable housing at a record pace, and rents were frozen for more than 2 million tenants. That is the Mayor’s record, and it is one that New Yorkers are rallying around,” said de Blasio campaign spokesman Dan Levitan.