Carl Campanile/New York Post

NEW YORK – The in-laws of state GOP Chairman Ed Cox are trying to knock off the only Republican Congressman in New York City – Staten Island Rep. Michael Grimm, The Post has learned.

Billionaire supermarket mogul John Catsimatidis and his family have pumped $19,800 into the campaign of Grimm’s Democratic challenger, Brooklyn Councilman Domenic Recchia, campaign records show.  The contributions to Recchia raised eybrows because Catsimatidis’ daughter, Andrea, is married to Cox’s son, Christopher.

Andrea Catsimatidis herself contributed $4,950 to Recchia’s campaign. John Catsimatidis just ran a spirited campaign for the GOP nomination for Mayor but lost to former MTA Chairman Joe Lhota.

A combined four donations were made to Recchia under the name of John A. Catsimatidis totaling $9,900. The Recchia campaign said the contributions came from Catsimatidis and his son, also named John. Catsimatidis’ wife, Margo, also kicked $4,950 into Recchia’s coffers.

Staten Island GOP sources were mystified by the Catsimatidis clan’s push for Recchia over the GOP incumbent. Grimm backed Lhota over Catsimatidis in the GOP primary, but the support was tepid.

“People on Staten Island are shocked. Not only because John ran for mayor as a Republican, but because of the Catsimatidis family ties to state GOP Chairman Cox. It’s bizarre,” an island GOP insider said.

Catsimatidis insisted his financial backing of Recchia was not payback to Grimm for backing Lhota for Mayor. “There’s no bad blood between me and Grimm,” Catsimatidis said. He said he’s known Recchia for years from his work on the Council, which is why he’s supporting him.

“[Recchia] is a terrific advocate for the community – the residential community and business community,” Catsimatidis said.

But Catsimatidis also said that Grimm requested a meeting with him a few weeks ago to clear to the clear the air, after hearing that the billionaire businessman donated to Recchia. He said Grimm told him that he backed Lhota as a debt to Rudy Giuliani.

Asked how he felt about trying to knock off the only Republican congressman from the city, Catsimatidis said, “Time will tell if I do anything further.” Recchia said the support of the Catsimatidis clan proved he’s not a one-party candidate.

“Domenic’s trusted reputation and proven record of achieving results for the people of Staten Island and South Brooklyn is attracting support from many of the city’s leading voices on both sides of the aisle. Our campaign is grateful to have the support of John Catsimatidis and his family,” said Recchia campaign spokeswoman Ashleigh Owens.

The congressional district covers all of Staten Island and much of southern Brooklyn. Recchia served as the Council’s finance committee chairman for many years and worked with Staten Island allies to deliver “pork” to the borough.

Grimm, an ex-marine and FBI agent, was first elected in 2010 and is seeking a third term. He narrowly won re-election last year against a weak Democratic opponent while fending off a Justice Department probe into his campaign fundraising activities. Grimm denies wrongdoing but the investigation is ongoing.