BOZEMAN (AP) — A Republican congressional candidate in Montana charged with shoving a reporter to the ground on the eve of a special election kept a low profile Thursday even as supporters prepared a hotel ballroom for a possible victory party.

Greg Gianforte was charged with misdemeanor assault after witnesses said he grabbed a reporter by the neck on Wednesday and threw him to the ground at Gianforte’s campaign headquarters in Bozeman.

Gianforte, a millionaire tech entrepreneur who has aligned himself with President Donald Trump, said the reporter was being aggressive and grabbed him by the wrist at his campaign office.

The altercation occurred hours before voters went to the polls to decide whether Gianforte or Democrat Rob Quist will fill the U.S. House seat vacated by Ryan Zinke, a Republican who is now Trump’s Interior secretary.

Many see the closely watched election as a referendum on the policies and practices of Trump.

Democratic Gov. Steve Bullock, who defeated Gianforte in November’s election, called Wednesday’s events “another wake up call to all Montanans and Americans that we must restore civility in politics and governing.”

Republicans have held the state’s lone congressional seat for two decades.

It wasn’t clear how the last-minute melee would affect the race. More than a third of the state’s registered voters had cast absentee ballots before polls opened Thursday.

Three of Montana’s biggest newspapers pulled their endorsements of Gianforte — without endorsing his opponent — while leaders of both major parties called on him to apologize.

House Speaker Paul Ryan, a Republican, said what occurred was “wrong and should not happen.” House Minority Leader Nancy Pelosi, a Democrat, called Gianforte “a wannabe Trump.”

“I don’t think it probably changed very many minds or votes today, unfortunately,” said voter Patrick Paradis, who supports Democrat Rob Quist. “Politics are pretty entrenched right now in terms of who people are going to follow and who people are going to vote for.”

Gianforte was preparing for an interview with Fox News on Wednesday at a private office when Ben Jacobs, a reporter for The Guardian, came in without permission, campaign spokesman Shane Scanlon said.

As Jacobs pressed the candidate on the GOP health care bill, “Gianforte grabbed Jacobs by the neck with both hands and slammed him into the ground behind him,” Fox News reporter Alicia Acuna wrote in an article . She added that Gianforte then began to punch Jacobs.

In an audio recording posted by The Guardian, the reporter asks the congressional candidate about the health care bill.

“We’ll talk to you about that later,” Gianforte says on the recording, referring Jacobs to a spokesman.

When Jacobs says there won’t be time, Gianforte says “Just--” and there is a crashing sound. Gianforte yells, “The last guy who came here did the same thing,” and a shaken-sounded Jacobs tells the candidate he just body-slammed him.

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

Gianforte’s whereabouts weren’t immediately known Thursday. Two people at his campaign headquarters in Bozeman referred all questions to Scanlon, who could not be reached. A sign on a gate thanked people for not trespassing at Gianforte’s home.

Repeated phone calls to Gianforte’s cellphone went unreturned. Twice it seemed someone picked up then immediately hung up.

Jacobs told ABC’s “Good Morning America” that he never touched Gianforte. He said of the politician’s account: “The only thing that is factually correct ... is my name and place of employment.”

Quist declined to comment on the incident.

Gallatin County Sheriff Brian Gootkin announced the misdemeanor assault charge shortly before midnight Wednesday in a written statement, about six hours after the incident.

Gianforte could face a maximum $500 fine or six months in jail if convicted; he’s due in court on or before June 7.

Gootkin said Jacobs’ injuries did not meet the legal definition of felony assault.

In Montana, assaults without a weapon are considered misdemeanors; assaults that cause serious physical injuries or involve weapons are treated as felonies.

Gootkin previously had contributed $250 to Gianforte’s campaign, according to elections records.