Sen. Charles Schumer’s brother-in-law was quietly nominated this month to a federal judgeship in New Jersey — a move that has some in the Garden State crying political foul, The Post has learned.

Kevin McNulty, who is married to Schumer’s sister, Fran, was named to the US District Court by the White House late on Friday, Dec. 16. According to a boilerplate quote, President Obama believes McNulty is a “distinguished individual” who “will serve the American people with integrity and a steadfast commitment to justice.”

New Jersey’s two US senators, Frank Lautenberg and Robert Menendez, followed that up with their own news release heaping praise on the nominee.

What no one mentioned is that McNulty, 57, was the last-minute choice of Lautenberg, who had been leaning toward other candidates until surprisingly submitting McNulty’s name to the White House.

Lautenberg and his aides have given no public explanation for the decision to go with McNulty even though the latter had never been publicly touted as a contender for the job, which carries life tenure and a $174,000-a-year salary.

“No one knows why he did it,” said one person involved in the nomination process. “Everyone thinks it’s all about 2014 and Frank making sure he has Chuck in his corner.”

The White House declined to comment, as did McNulty.

Lautenberg’s reps denied any political motives and stressed that McNulty, who lives in upscale Short Hills, won the nod on the merits. He is a senior partner at Gibbons PC in Newark.

Aides also insisted that Lautenberg was clueless about McNulty’s relationship to Schumer when he first looked at him in 2009.

“It is complete fiction to suggest that there was any deal or that Kevin McNulty was brought into the process at the last minute,” said Lautenberg spokesman Caley Gray.

People involved in the judicial-nomination process in New Jersey told The Post they believe the surprise nomination was a naked political maneuver by the 87-year-old Lautenberg to stay in Schumer’s good graces. Lautenberg is worried that party elders will try to push him out of his beloved Senate seat because of his advanced age — something that Schumer, one of the party’s top opinion makers and fund-raisers, would be able to stop.

“McNulty came out of left field,” said another source involved in the Jersey judicial politics. “McNulty’s not a dumb guy, but people were just, like, ‘How’d that happen?’ ”

Schumer spokesman Mike Morey said Schumer played no part in his brother-in-law’s nod. He insisted Lautenberg could never lose Schumer’s backing.

“Chuck Schumer has supported Frank Lautenberg through thick and thin, both in primaries and general elections,” Morey said. “It’s laughable to think he wouldn’t support him in the future.”