It is an astonishing development in an important congressional race.

The Republican candidate for Montana's lone seat in Congress is locked in a tight race with a come-from-behind Democratic candidate. And the special election is Thursday.

And the GOP candidate, Greg Gianforte, was today preparing for a local TV interview when a reporter from the Guardian newspaper in London, started asking questions.

The reporter, Ben Jacobs, was asking about today's Congressional Budget Office report on the Republican alternative health care act.

That's when Gianforte, according to the reporter and other witnesses, slammed Jacobs to the ground and stood over him yelling that he was "sick and tired of this."

The altercation was captured on audio tape and the Guardian has released the recording. It contains this shouted exchange.

“I’m sick and tired of you guys,” Gianforte says. “The last time you came here you did the same thing. Get the hell out of here!”

“J***s C****t,” Jacobs said. “You just body slammed me and broke my glasses.”

“Get the hell out of here,” Gianforte says again.

”If you’d like me to get the hell out of here, I’d also like to call the police,” Jacobs says. 

The local TV team confirmed the reporter's account and the Fox reporter said that Jacobs was never aggressive in the incident.

Gianforte's campaign claimed the guardian reporter, a "liberal journalist," grabbed the candidate's arm, and that started the confrontation.  The Gallatin County Sheriffs Office has taken statements from the Fox crew and others in the room.

While the incident may have an effect on tomorrow's vote, most of the state's ballots have already been cast early. Gianforte is locked in a tight race with Rob Quist, a banjo-playing folk musician, first-time candidate.