Gianforte appeared in Gallatin County Justice Court, where Judge Rick West ordered him to serve 40 hours of community service, attend 20 hours of anger management sessions and pay $385 in fines.
Those penalties were in lieu of a 180-day jail sentence, which was deferred. If the wealthy businessman completes the conditions under his sentence, he will be eligible to petition for the conviction to be removed from his records.
West initially had sentenced Gianforte to four days, with a stipulation that the congressman-elect could participate in a work program as an alternative to jail, but quickly changed the sentence when he learned that Gianforte was not eligible for the work program.
"You accepted responsibility. You apologized," West told Gianforte in the crowded courtroom packed with journalists and spectators.
During the hearing, reporter Ben Jacobs of the Guardian, a British newspaper with an international web readership, recounted his violent encounter with Gianforte and the subsequent national ramifications.
"While I have no doubt that actions like these were an aberration for Congressman-elect Gianforte personally," Jacobs said in his trial statement, "I worry that, in context of our political debate, they have become increasingly common. There will always be fundamental political disagreements in our society. However, these need not become personal and certainly should never become violent."
Gianforte apologized to Jacobs. "I just want to say I'm sorry," he said as he stood behind a lectern at the front of the courtroom. "If and when you are ready, I look forward to sitting down with you in D.C."
Gianforte attacked Jacobs on May 24 when the reporter asked him a healthcare policy question at his campaign headquarters in Bozeman. Gianforte began shouting at Jacobs to leave, then body-slammed him to the ground, breaking his glasses.
The following day, Gianforte defeated Democrat Rob Quist, a professional bluegrass musician making his first run for public office. They were running for the seat vacated by Republican Ryan Zinke, who left to accept an appointment as Interior secretary.
Gianforte's campaign initially denied any culpability and blamed Jacobs for the altercation. However, a Fox news crew was in the room at the time, and corroborated Jacobs' account of the assault.
After his sentencing, Gianforte avoided questions about why his campaign had falsely accused Jacobs of the assault.
However, he did say: "I take full responsibility for my action. I didn't act in a way that was consistent with my behavior in the past. That's why I was pleased to be here and get this done and move forward."
As part of a civil settlement last week, Jacobs agreed not to sue the 56-year-old politician and Gianforte said he would donate $50,000 to the nonprofit Committee to Protect Journalists. Gianforte also apologized to Jacobs then.
Gianforte is expected to be sworn in later this month, but some Montana Democrats are urging him to resign. "The people of Montana need a representative in Congress," Nancy Keenan, executive director of the Montana Democratic Party, said in a statement. "They do not need a criminal. Gianforte should not be sworn in as a member of Congress, and if he is, he must resign."
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1:55 p.m.: This article was updated with additional quotes, background.