“Get the hell out of here,” Mr. Gianforte said again. Mr. Jacobs said he would report the episode to authorities and asked for the names of the other individuals in the room. Then the tape ends.
In a statement, Mr. Gianforte’s spokesman offered a strikingly different version of events — and one at odds with Mr. Jacobs’s recording.
“After asking Jacobs to lower the recorder, Jacobs declined,” said Shane Scanlon, Mr. Gianforte’s spokesman. “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.”
Mr. Gianforte is not heard on the recorder requesting that Mr. Jacobs lower the recorder.
A second reporter present, BuzzFeed’s Alexis Levinson, suggested it was Mr. Jacobs who was under attack.
“Ben walked into a room where a local TV crew was set up for an interview with Gianforte,” Ms. Levinson wrote on Twitter. “All of a sudden I heard a giant crash and saw Ben’s feet fly in the air as he hit the floor.”
Mr. Gianforte never spoke at his own event, witnesses said, remaining behind closed doors and leaving after local police officers arrived, well before the gathering was supposed to conclude.
Ms. Levinson said officers took statements from witnesses.
In a telephone interview from a Bozeman hospital where he was getting an X-ray on his elbow, Mr. Jacobs said Mr. Gianforte was the sole aggressor.
“I landed on my elbow on a concrete floor,” he said.
Mr. Jacobs said Mr. Gianforte had been angry about a video about the campaign The Guardian posted Tuesday.
Before getting off the phone, Mr. Jacobs had a request for a reporter about the altercation: “Wait till my piece goes up, don’t scoop me on this.”
Three hours to the west, in Missoula, Rob Quist, the Democratic nominee for the seat, which was vacated by Interior Secretary Ryan Zinke, seemed taken by surprise when he was asked about the altercation.
“That’s really not for me to talk about; I think that’s more a matter for law enforcement,” Mr. Quist said.
But the House Democratic campaign arm quickly seized on the episode, calling on Mr. Gianforte to “immediately withdraw” from the race.
Mr. Gianforte ran for governor in Montana last year, his first bid for office after amassing a fortune as a technology executive.
Earlier Wednesday, after a rally in Helena, he spoke briefly with this reporter in between greeting supporters. He immediately turned to his spokesman when approached, but did respond to a question about the role of President Trump in the race.
The news of the altercation quickly spread on social media Wednesday evening, but it is an open question whether it will affect the outcome of the race. Over 250,000 Montana voters have already cast their ballots by mail here, a figure officials in both parties say amounts to well over half of the total turnout.
While Montana is a Republican-leaning state and Mr. Gianforte has been enjoying an advantage in private polling here, the campaign of Mr. Quist, a banjo-strumming folk singer, has caught fire with national progressive activists. He raised over $6 million despite receiving scant help from Democrats in Washington. Much of that money, though, came in well after Republicans had been on the air here assailing Mr. Quist.
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