"I should not have responded the way I did, and for that I'm sorry", Gianforte said.
"He took me to the ground", Jacobs told his newspaper by phone from inside an ambulance. In Montana, Gianforte is on pace to win by about 6 points, underperforming by 14 points.
With a majority of the precincts reporting, Gianforte led by a 49-44 margin.
A Democratic upset in the race would set off alarms for Republicans already anxious about the effects of Trump's unpopularity and the healthcare issue on their candidates in next year's midterm elections, when Republicans must defend their 24-seat House majority. Quist emphasized issues like healthcare during the race, and refrained from commenting on the incident.
Quist, wearing his signature cowboy hat, told supporters in Missoula, Montana, that the grassroots energy of his campaign would continue.
The news comes a little more than 24 hours after the former failed gubernatorial candidate allegedly assaulted a reporter for the Gaurdian by bodyslamming him in front of witnesses while being recorded by audiotape.
Approximately a third of Montana's eligible voters had cast absentee ballots before Gianforte was cited Wednesday by the Gallatin County Sheriff's Office following a confrontation with Guardian reporter Ben Jacobs.
If Gianforte wins the election: "I don't think I'd feel real good about it", said another customer, Richard House, who declined to say whom he voted for.
Three local newspapers have since withdrawn their endorsements for Gianforte.
After his victory was announced, Gianforte addressed his attendees.
"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.
In another statement, Governor Steve Bullock said, "It is unsettling on many levels that Greg Gianforte physically assaulted a journalist and then lied, refusing to take responsibility for his actions".
"Montana sent a strong message tonight that we want a Congressman that will work with President Trump to make America and Montana great again", he said.
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.
Republican lawmakers criticized Gianforte but stopped short of asking him to withdraw from the race. He collected almost $3.2 million from individual donors across the U.S.
At a evening news conference, Gallatin County Sheriff Brian Gootkin said deputies were interviewing Jacobs, had obtained a copy of his audio recording, and had spoken briefly to Gianforte at the scene before he left.
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