A Montana Republican congressional candidate has been charged with misdemeanor assault for allegedly body-slamming a reporter who was trying to ask him a question Wednesday on the eve of a special election, law enforcement said.

Greg Gianforte — a tech millionaire who was nominated by the GOP to run for an open seat — faces up to six months in jail, after the Gallatin County Sheriff’s Office decided they had probable cause to cite him for an attack on reporter Ben Jacobs of The Guardian.

Jacobs was trying to ask the Republican a question about the Congressional Budget Office’s estimates about the GOP health bill when Gianforte flew into a rage and allegedly threw him to the floor, breaking the journalist’s glasses.

The alleged assault happened at the Republican’s campaign headquarters in the city of Bozeman, right before he was set to give an interview to a local news station.

“Greg Gianforte just body slammed me and broke my glasses,” tweeted Jacobs, political reporter for The Guardian.

The outlet later posted audio of the scuffle, which unfolded around 6 p.m., according to the Bozeman Daily Chronicle.

Authorities reportedly responded and rushed Jacobs to a local hospital.

“He took me to the ground,” Jacobs told his colleagues at The Guardian by phone, while sitting in the back of an ambulance.

“This is the strangest thing that has ever happened to me in reporting on politics,” he said.

In the audio clip, Gianforte can be heard arguing with Jacobs — right before a loud crashing sound is heard.

“Get the hell out of here,” Gianforte says repeatedly. “The last guy did the same thing. Are you with The Guardian?”

Jacobs replied: “Yes! You just broke my glasses.”

Gianforte responded, “The last guy did the same damn thing.”

“You just body-slammed me and broke my glasses,” Jacob yelled.

“Get the hell out of here,” Gianforte seethed.

A crew from Fox News reportedly saw the drama unfold and claimed Gianforte not only slammed Jacobs, but grabbed him by the neck and began punching him. But neither cops nor the reporter ever claimed this happened.

The Gianforte campaign later released a statement, insisting he was innocent.

“As Greg was giving a separate interview in a private office, The Guardian’s Ben Jacobs entered the office without permission, aggressively shoved a recorder in Greg’s face, and began asking badgering questions,” a spokesperson said, despite there being no audio evidence that this happened.

“Jacobs was asked to leave. After asking Jacobs to lower the recorder, Jacobs declined. Greg then attempted to grab the phone that was pushed in his face. Jacobs grabbed Greg’s wrist, and spun away from Greg, pushing them both to the ground. It’s unfortunate that this aggressive behavior from a liberal journalist created this scene at our campaign volunteer BBQ.”

The local sheriff’s office said that after talking to all witnesses, they decided the incident “did not meet the statutory element of felony assault,” and decided to cite him on misdemeanor charges.

They said Gianforte “received a citation on Wednesday night and is scheduled to appear in Gallatin County Justice Court between now and June 7, 2017.”

Sheriff Brian Gootkin also defended himself after reports came out that he was a donor to the Gianforte campaign.

“I did contribute $250.00 on March 23, 2017,” he wrote in a press release. “This contribution has nothing to do with our investigation which is now complete.”

Gianforte, a noted hunting buddy of Donald Trump Jr., made headlines last year when he failed to beat incumbent Democrat Steve Bullock in the election for Montana governor — despite the state voting largely in favor of President Trump. The state also gave a big win to former GOP Rep. Ryan Zinke, who left the seat open when he became Trump’s secretary of the interior.

Gianforte is leading in polls against Democrat Rob Quist, a popular Montana folk singer and banjo player. But some polls show Quist withing striking distance in the deeply red state.

The Democratic Congressional Campaign Committee called on Gianforte to back out of the congressional race Wednesday night following the incident.

“Greg Gianforte must immediately withdraw his candidacy after his alleged violent assault of an innocent journalist,” they said in a statement. “Further, Speaker Ryan and the National Republican Campaign Committee should not waste another minute before publicly denouncing their candidate and apologizing for the millions of dollars they spent on his behalf.”

With Post wires