Republican Greg Gianforte celebrates with supporters after being declared the winner at a election night party for Montana's special House election against Democrat Rob Quist at the Hilton Garden Inn on May 25, 2017 in Bozeman, Montana.

Republican Greg Gianforte declared victory in Montana's special congressional election, barely a day after he was charged with misdemeanor assault following accusations that he slammed a journalist to the ground.

Gianforte, 55, a technology entrepreneur, held a 50 percent-to-44 percent lead over Democrat Rob Quist shortly after 12 a.m. ET, with nearly half of precincts reporting. Libertarian Mark Wicks had 6 percent; his vote total was less than Gianforte's margin over Quisp.

"Tonight Montanans are sending a message to the Washington, D.C., establishment," Gianforte told a cheering crowd in Bozeman about 12:45 a.m. ET.

"Last night, I made a mistake, and I took an action that I can't take back," Gianforte said, addressing the controversy publicly for the first time. "I should not have treated that reporter that way, and for that, I am sorry, Mr. Ben Jacobs."

"And I'm sorry to each one of you that we had to go through this," he added. "You deserve a congressman who stays out of the limelight and just gets work done."

The Associated Press declared Gianforte the winner early Friday.

Gianforte, 55, a technology entrepreneur, had been leading Quist and Wicks in opinion polls before Wednesday night, when Ben Jacobs, a reporter for The Guardian, accused Gianforte of having "body slammed" him at a campaign event.

Gianforte denied the allegation, accusing Jacobs of having been the aggressor. A Fox News Channel crew who witnessed the confrontation backed Jacobs' version of events.

Democrats demanded that Gianforte withdraw from the race for the U.S. House seat left vacant after Republican Rep. Ryan Zinke became President Donald Trump's interior secretary.

But the incident came after an estimated two-thirds had already cast their ballots by mail — and none were allowed to change their votes after news of the confrontation broke.

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