Although Gianforte has denied wrongdoing, several Montana news outlets withdrew their endorsements of his candidacy and reconsidered past situations in which Gianforte seemed to express aggression toward reporters.
An editorial in the Helena Independent Record described the paper as "sick and tired of Gianforte's incessant attacks on the free press."
"In the past, he has encouraged his supporters to boycott certain newspapers, singled out a reporter in a room to point out that he was outnumbered, and even made a joke out of the notion of choking a news writer, and these are not things we can continue to brush off," the paper's editorial staff wrote Thursday.
Last month, a voter at a Gianforte town hall pointed out a journalist in the room, called the media "the enemy" and mimed the act of wringing a neck.
Gianforte smiled and pointed at the reporter.
"We have someone right here," he said, according to the Ravalli Republic. "It seems like there are more of us than there is of him."
Gianforte appeared to have the edge in his race against Democrat Rob Quist for Montana's only House seat before Wednesday night's incident threw the race into turmoil. The campaign pitted Gianforte, a onetime gubernatorial candidate whose net worth has been estimated at nearly $200 million, against Quist, 69, a cowboy-poet and musician with a history of unpaid taxes who had never run for office.
Some political strategists had acknowledged that Gianforte's strong personality was becoming an issue in the race, as it had during his unsuccessful gubernatorial bid in 2016.
"As soon as Greg started getting attacked on TV, people were like, 'Oh, yeah, that guy, [the] billionaire jerk from New Jersey,' " an unnamed Republican strategist familiar with the race told Roll Call this week.
Gianforte fully embraced President Trump during his congressional bid. He has campaigned with Vice President Pence and Donald Trump Jr. and spent time hunting — a favorite pastime — with the latter.
According to some critics, he has even channeled the president's tough-guy persona.
Gianforte is a "wannabe Trump," House Minority Leader Nancy Pelosi (D-Calif.) told reporters Thursday on Capitol Hill.
"To use language like that, treat people harshly like that — that's his model," she said. "Donald Trump's his model. And we've really got to say, 'Come on. Behave. Behave. That's outrageous.' "
Gianforte was born in San Diego and spent his formative years in the Philadelphia suburbs before receiving degrees in electrical engineering and computer science from the Stevens Institute of Technology in Hoboken, N.J.
He started his career at AT&T Bell Laboratories in 1983. By his mid-30s, Gianforte had retired to Montana after selling his first software company, BrightWork Development, to nascent software giant McAfee for more than $10 million, according to Inc., a monthly business magazine.
A few years later, in 1997, he started his second technology venture, RightNow Technologies, providing customer service software. Oracle acquired the company in 2011 for a reported $1.5 billion. Gianforte received more than $100 million from the sale, a figure that brought his total income between 2005 and 2014 to $220.5 million, according to an Associated Press review of his tax returns.
During his time running RightNow, Gianforte became close to colleague Steve Daines, now Montana's junior senator. Daines, a Republican and one of Gianforte's closest allies in state politics, has called on him to apologize for Wednesday's incident.
Gianforte first considered living in Montana during a hiking trip to the state in junior high school. Since moving there in the mid-1990s, he and his wife, Susan, have become part of the fabric of life in Bozeman, with their interest in technology start-ups, evangelical Christian faith and conservative political beliefs defining their ties to the community, according to news reports.
Their philanthropy and activism have not come without controversy. Gianforte was a significant funder of the creationist Dinosaur and Fossil Museum in Glendive, Mont., which presents exhibits on the Earth's age and the origins of the dinosaurs "in the context of biblical history."
Speaking at the Montana Bible College in 2015, Gianforte raised eyebrows for his comment that "the concept of retirement is not biblical."
"The example I think of is Noah," he said, according to the HuffPost. "How old was Noah when he built the ark? Six hundred. He wasn't, like, cashing Social Security checks, he wasn't hanging out, he was working. So, I think we have an obligation to work."
Gianforte also lobbied against an LGBT anti-discrimination ordinance in Bozeman in 2014, suggesting in an email to city officials that allowing discrimination based on sexual orientation would be good for the local economy.
"Homosexual advocates try to argue that businesses are leery of locating in towns that aren't friendly to homosexuals. I believe the opposite is truer," Gianforte wrote in the email, obtained in 2015 by the National Journal.
During his 2016 race for Montana governor, Gianforte sought to clarify his position on the measure in a meeting with the editorial board of the Billings Gazette. He "endorsed nondiscrimination for workers . . . but not for customers," the paper wrote.
These views have complicated the Gianfortes' relationships in the world of higher education. In 2014, Montana Tech, a state-run university in Butte, announced that the couple would be its commencement speakers, prompting a backlash from students and faculty members.
Two years later, the Montana Board of Regents faced similar protests while considering an $8 million donation from the Gianfortes that would involve naming a university department after them. The board ultimately accepted the gift and approved the name change.
Gianforte's sale of RightNow in 2011 ushered in a period of intense involvement in conservative education causes for the former executive. At the time, he was already a decade into a 14-year tenure as chairman of the board of Petra Academy, a K-12 Christian school in Bozeman that his children attended. The family donated $11.1 million to the school between 2005 and 2013 through its private foundation.
In 2012, Gianforte joined the boards of the Association of Classical and Christian Schools, the Friedman Foundation for Educational Choice, and ACE Scholarships, all of which advocate for school choice. Several of these groups received substantial donations from the Gianfortes, as did a variety of organizations that promote conservative Christian views such as opposition to abortion and same-sex marriage. Those groups included Focus on the Family, the Montana Family Foundation, Montana Right to Life, Alliance Defending Freedom, and the American Center for Law and Justice.
The Gianforte Family Foundation, founded in 2004, had $113 million in assets in 2013, according to a review published last year in the Billings Gazette. Gianforte sought to deflect attention to these donations during his 2016 gubernatorial campaign, presenting himself as a successful businessman and a proponent of Montana's small technology community, not a conservative activist.
"I think prosperity is a virtuous thing and we need more of it in Montana," he said in early 2016, before entering the race, according to the Associated Press.
Gianforte has served as the managing director of the Bozeman Technology Incubator since 1995, according to his LinkedIn profile, and is a member of FICO's corporate board.
An avid hunter who regularly posts trophy photos on social media, Gianforte drew media attention last month for his plans to shoot prairie dogs with Trump Jr. while he was in Montana.
"As good Montanans, we want to show good hospitality to people,'' Gianforte said, according to the Associated Press. "What can be more fun than to spend an afternoon shooting the little rodents?''
He dismissed concerns voiced by the Humane Society of America. "Clearly they've never shot a prairie dog," Gianforte said. "They don't know how much fun it is."
Alice Crites contributed to this report.