MISSOULA, Mont. — The Republican candidate in a hotly contested special House election in Montana was charged with assaulting a journalist on Wednesday at what was to be a final rally in Bozeman on the eve of the vote. The attack brought police officers to the event and sent the reporter to the hospital for X-rays.
In a statement late on Wednesday, the office of the Gallatin County sheriff, Brian Gootkin, said that there was enough evidence to charge the candidate, Greg Gianforte, with misdemeanor assault. Mr. Gianforte, the Republican candidate for the state’s lone House seat, is scheduled to appear in court before June 7.
It was an extraordinary development in a race that was being closely watched for clues about the national political environment in the tumultuous first months of the Trump presidency.
In a sign of the considerable Republican frustration with Mr. Gianforte, Speaker Paul D. Ryan publicly scolded the candidate and said he should apologize. Mr. Ryan said that the “physical altercation” was inappropriate and “should not have happened.”
“Should the gentleman apologize? Yeah, I think he should apologize,” Mr. Ryan said. “I know he has his own version and I’m sure he’s going to have more to say, but there’s no call for this, no matter what — on any circumstance.”
But Mr. Ryan indicated that he would not seek to block Mr. Gianforte from taking office in the event that he wins. Should that happen, Mr. Ryan said, then “he has been chosen by the people of Montana.”
Representative Steve Stivers of Ohio, the chairman of the National Republican Congressional Committee, released a gentler statement on Mr. Gianforte’s apparent eruption, describing it as “totally out of character” and conceding that “we all make mistakes.” But the Montana election, Mr. Stivers said, “is bigger than any one person.”
Three of the state’s largest newspapers, The Billings Gazette, The Missoulian and The Independent Record, quickly rescinded their endorsements of Mr. Gianforte. But prospects that the altercation could tip the race to the Democrat, Rob Quist, were complicated by Montana’s early-voting tradition: Over half the estimated total ballots in the contest had been returned by Wednesday.
Ben Jacobs, a reporter for The Guardian, said the episode occurred during an interview at Mr. Gianforte’s campaign headquarters. Mr. Jacobs said Mr. Gianforte “body-slammed” him when pressed on a question about the Republicans’ health care bill.
Members of a Fox News television crew witnessed the encounter, and in a firsthand account posted on the network’s website, one of the Fox journalists described Mr. Gianforte as “punching the reporter.”
“As Gianforte moved on top of Jacobs, he began yelling something to the effect of, ‘I’m sick and tired of this!’ ” according to the Fox News account.
Mr. Jacobs said Mr. Gianforte became agitated when asked about the Congressional Budget Office’s new fiscal assessment of the legislation that House Republicans have passed to repeal the Affordable Care Act.
Mr. Gianforte initially sidestepped the question, according to an audio recording of the episode Mr. Jacobs posted, suggesting the reporter speak with his spokesman. But when Mr. Jacobs persisted, the candidate lost his composure.
“I’m sick and tired of you guys!” Mr. Gianforte can be heard saying on the recording shortly after the sounds of a physical struggle and a crash. “The last time you came here you did the same thing. Get the hell out of here. Get the hell out of here.”
Mr. Jacobs responded: “You just body-slammed me and broke my glasses.”
“Get the hell out of here,” Mr. Gianforte said again. Mr. Jacobs said he would report the episode to the authorities and asked for the names of the other individuals in the room. Then the tape ends.
The Republican nominee has been sensitive about health care questions since he was caught on tape this month telling Washington lobbyists on a conference call that he was “thankful” the House voted to repeal the health law. Mr. Gianforte had been indicating to voters that he would not support the bill without knowing its cost — precisely the question answered by the C.B.O. score.
In a statement, Mr. Gianforte’s spokesman offered a strikingly different version of events.
“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 recording requesting that Mr. Jacobs lower the recorder.
Another witness, BuzzFeed’s Alexis Levinson, wrote on Twitter, “Ben walked into a room where a local TV crew was set up for an interview with Gianforte.” She added, “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.
If convicted, Mr. Gianforte faces up to a $500 fine, or six months in jail, or both.
Three hours to the west, in Missoula, Mr. Quist, the Democratic nominee for the seat, which was vacated by Ryan Zinke when he became the Interior Department secretary, seemed taken by surprise when he was asked about the episode.
“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.
The newspapers were swift in withdrawing their endorsements of the Republican candidate, with The Missoulian saying that Mr. Gianforte “should lose the confidence of all Montanans.”
The Billings Gazette’s editorial board released a blistering statement. The board’s members said they were “at a loss for words.”
“We will not stand by that kind of violence, period,” The Gazette said.
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 a reporter in between greeting supporters. He immediately turned to his spokesman when approached, but he did respond to a question about the role of President Trump in the race.
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 little help from Democrats in Washington.
Much of that money, though, came in well after Republicans had been on the air here criticizing Mr. Quist.
After the incident, Mr. Jacobs had journalism on his mind during a telephone interview from the Bozeman hospital where he was getting an X-ray on his elbow.
“Wait till my piece goes up,” he asked before getting off the phone. “Don’t scoop me on this.”