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WASHINGTON — House Speaker Paul Ryan on Thursday called on Republican Greg Gianforte to apologize after he was charged with assaulting a reporter, but said he will leave it up to Montana voters to decide whether they want him to serve in Congress.

"I do not think this is acceptable behavior, but the choice will be made by the people of Montana,” Ryan said during a press conference. "I think he should apologize."

A Montana sheriff charged Gianforte with misdemeanor assault Wednesday night after Guardian journalist Ben Jacobs said the politician "body slammed" him at a campaign event in Bozeman while the reporter tried to ask a question.

The incident occurred hours before polls opened Thursday in the high-profile race between Gianforte and Democrat Rob Quist for the state’s open House seat.

Democrats immediately demanded Gianforte withdraw from the race, while three of the state’s largest newspapers rescinded their endorsements of the GOP candidate.

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But a defiant Gianforte portrayed himself as the victim, with a spokesperson blaming the “aggressive behavior from a liberal journalist."

Republicans for the most part stood by Gianforte, with several telling reporters he would be welcome on Capitol Hill.

"We all make mistakes," said Ohio GOP Rep. Steve Stivers, the chairman of the National Republican Congressional Committee. “From what I know of Greg Gianforte, this was totally out of character."

Montana Sen. Steve Daines, one of Gianforte's biggest supporters, called on the candidate to apologize and said he would leave it up to law enforcement. "I do not condone violence in any way," he said.

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A source close to the Gianforte campaign told NBC News they raised over $100,000 online in the 24 hours, with most of the donations coming after the incident.

Jacobs told MSNBC's Chris Hayes that he was trying to ask Gianforte about the Congressional Budget Office's financial analysis of the Republican health care plan when "the next thing I know, I'm being body-slammed."

"He's on top of me. My glasses are broken," Jacobs said. "It's the strangest moment that's happened in my entire life reporting."

Jacobs' claims were supported by an audio recording of the event and an eyewitness account by a Fox News crew that happened to be in the same room.

Greg Gianforte just body slammed me and broke my glasses — Ben Jacobs (@Bencjacobs) May 24, 2017

Sheriff Brian Gootkin held a press conference Thursday afternoon to say the matter had now been turned over the country prosecutor ahead of Gianforte's June 7 court date and that the incident did not merit a felony assault charge because Jacobs "was not seriously injured."

Gootkin also said Gianforte refused to give a statement to authorities and was never arrested.

"He left the scene and deputies were busy talking to witnesses and the victim," added Gootkin, who also dismissed questions about potential conflicts of interest after it was revealed he had donated $250 to Gianforte's campaign.

In a statement, Shane Scanlon, a spokesman for Gianforte's campaign, alleged that Jacobs started the kerfuffle when he crashed an interview the Republican candidate was preparing to give to another media outlet.

"It's unfortunate that this aggressive behavior from a liberal journalist created this scene at our campaign volunteer BBQ," he said.

Jacobs dismissed that version of events. "The only thing in the Gianforte statement that is factually correct is my name and my place of employment," Jacobs said on ABC's "Good Morning America" Thursday.

In a statement, Lee Glendinning, The Guardian's U.S. editor, said that the newspaper was "deeply appalled" and that "we stand by Ben."

Gianforte sitting in a Jeep. Sheriff's deputies were talking to him earlier. Now a medic is at the window talking with him. #bdcnews #mtal pic.twitter.com/JsT4tTYt82 — Whitney Bermes (@wabermes) May 24, 2017

Polls in the race have consistently shown Gianforte favored to retain the statewide congressional seat vacated by Interior Secretary Ryan Zinke. Quist, a folk singer, has come within striking distance thanks to an outpouring of money and energy from Democrats desperate to score a victory against Trump.

But the incident likely came too late to have any major impact on Thursday's election, since up to two-thirds of voters are estimated to have already cast a ballot in the race.

The front pages voters in Montana are waking up to on Election Day. pic.twitter.com/gaR7gGbOMM — Alex Seitz-Wald (@aseitzwald) May 25, 2017

Quist has so far said little about his opponent's physical altercation. “I’m just focused on the issues that are facing the people of Montana," he told reporters during a final campaign stop Wednesday night.

But other Democrats tried to capitalize on the moment. Several party-aligned groups have been running Facebook advertisements on the incident aimed at Montanans who may not yet have voted.

Democratic National Committee Deputy Chair Keith Ellison told NBC News Gianforte should withdraw from the race so he can “focus on his legal problems.”

Republican congressional candidate Greg Gianforte talks with supporters during a campaign event Wednesday in Missoula, Montana. Justin Sullivan / Getty Images

In audio of the confrontation posted to YouTube by The Guardian, a voice said to be Gianforte's asks Jacobs to speak with an aide. Then loud crashing sounds can be heard.

"I'm sick and tired of you guys! The last time you came in here you did the same thing. Get the hell out of here! Get the hell out of here!" the man yells.

So I was there for this - still am https://t.co/tgjOCYErFi — Alexis Levinson (@alexis_levinson) May 24, 2017

Gianforte and Jacobs have a history: Last month, Jacobs reported that Gianforte owns about $250,000 in shares in two index funds that have investments in Russian companies that are under U.S. sanctions.

CORRECTION (May 25, 2017, 8:10 a.m.): An earlier version of this article incorrectly stated that President Donald Trump visited Montana to support Greg Gianforte's campaign. The president has not done so, but his son, Donald Trump Jr., has.