But Gianforte cuts a sometimes-controversial profile, and while Democrats fear the impact his money could have on the race, he also has a long and socially conservative record they're eager to pick apart.
Gianforte has never sought elected office before, but he has a long paper trail from involvement in politics as a donor to various Christian and conservative causes.
Gianforte has been a strong supporter of local Christian schools and religious education initiatives, and he was one of the main funders behind a "creation museum" in Glendive, Mont., that bills itself as the "largest dinosaur and fossil museum in the United States to present its fossils in the context of biblical creation." According to the museum's exhibits, the Earth is no more than 6,000 years old, and dinosaurs and people coexisted before the Noah's biblical great flood.
"I don't think most people think that's acceptable," said Dave Hunter, a veteran Montana Democratic operative. "It's tolerable for a wealthy, eccentric businessman, but for a chief executive who's going to make a substantial portion of the decisions about what gets funded in education, or education initiatives, it makes me think it's going to be a real problem for him."
Gianforte has also contributed at least half a million dollars to the Montana Family Foundation, a conservative nonprofit that opposes abortion and same-sex marriage, and has positioned himself as a fierce supporter of so-called religious-freedom measures. Emails sent by Gianforte to Bozeman officials, and obtained by National Journal, show he personally lobbied against a citywide LGBT nondiscrimination ordinance in Bozeman in 2014.
In one January 2014 email sent to Bozeman Mayor Jeff Krauss and Bozeman city council members, Gianforte wrote, "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 urged them to consider the impact a nondiscrimination ordinance would have on Christian businesses. He attached a template for a "Religious Freedom Restoration Act," the same type of law that caused recent outcry in Indiana, which he thought could be substituted in place of the original nondiscrimination measure.
"No one wants discrimination in our community, but let's not throw safety to the wind, trample religious freedom, open the city up to expensive law suits and drive Christian businesses and organizations away from Bozeman in the process," Gianforte concluded.
In a second email two months later, Gianforte offered edits to a draft version of the nondiscrimination law that incorporated religious-conscience exemptions, including the right of any "faith-based university, college or post-secondary school" to deny student housing to married same-sex couples, "regardless of whether those couples are legally married." Gianforte also advocated for the right of religious organizations to "make employment decisions consistent with their faith," while noting that such protections should not allow "non-expressive" businesses to deny services to LGBT customers.