In Montana, an at-large congressional district special election was held on May 25, 2017, to determine the member of the United States House of Representatives for Montana's at-large congressional district. The election was necessitated by incumbent Republican Representative Ryan Zinke's appointment as United States Secretary of the Interior. Zinke resigned on March 1, 2017, upon his confirmation.
Montana's state law required the Governor of Montana to call for a special election to be held no less than 85 and no more than 100 days after the vacancy. Governor Steve Bullock declared a special election to take place on May 25, the earliest possible day he was legally allowed to choose.
The Democratic, Republican, Libertarian, and Green Parties held nominating conventions to decide their nominee. The day before the election, Gianforte assaulted a reporter and was charged with misdemeanor assault. At around 10:30pm MST, the election was called for Gianforte after 77% of the votes were counted.
Republican Party.
The Republican Party nominated a candidate at a convention on March 6.
Democratic Party.
The Democratic Party selected a nominee at a convention on March 5.
The Bozeman Daily Chronicle from February 4 to 8 conducted a straw poll of Democratic delegates. Of 89 delegates that responded, Rob Quist was selected by 37, Amanda Curtis by 30, Kelly McCarthy by 13, 9 were undecided, and zero delegates selected John Meyer or other.
Endorsements (primary).
 ;templatestyles src="Endorsements box/styles.css"/ ;Kelly McCarthy
 ;templatestyles src="Endorsements box/styles.css"/ ;Rob Quist
 ;templatestyles src="Endorsements box/styles.css"/ ;Dan West
Libertarian Party.
The Libertarian Party Convention on March 11, 2017, was held at Eagle's Lodge in Helena, Montana.
The following county affiliate parties were represented at the convention:
Officers of the Montana Libertarian Party and delegates from the assembled counties had voting rights.
Green Party.
The Green Party Convention on March 4, 2017, was held at the University of Montana's Payne Family Native American Center.
Breck, along with two independent candidates, won a lawsuit in U.S. District Court against the Montana Secretary of State, ruling Montana's ballot access laws to be unconstitutional in the case of special elections. The District Court Judge ruled to change the original requirement to submit 14,268 ballot petition signatures, reducing that requirement to 400 signatures. The US Court decision failed to provide further remedy and Breck's name was not placed on the ballot despite injunctive appeals to the Ninth Circuit Court and U.S. Supreme Court. Breck subsequently endorsed Independent write-in candidate Doug Campbell who was a co-plaintiff in the suit.
General election.
Campaign.
During his 2017 Congressional special election campaign, Gianforte relaxed his past pledges to refuse all PAC money, and began to turn away only corporate PAC funding. His campaign began accepting contributions from political party and leadership PACs.
The night before the election, Gianforte physically assaulted Ben Jacobs, a reporter from "The Guardian", in front of multiple witnesses, knocking him down, punching him, and breaking his glasses. Gianforte was subsequently charged with misdemeanor assault. The editorial boards of the "Billings Gazette", the "Independent Record", and the "Missoulian" rescinded their endorsements of Gianforte.
The Gianforte campaign released a statement following the incident alleging the incident was caused by, "this aggressive behavior from a liberal journalist", a claim contradictory to the eyewitness account of the Fox News team present in the room at the time. Alicia Acuna, one of two Fox news reporters present, and the only eyewitnesses to the incident, stated that Jacobs had walked into the room, put a voice recorder up to Gianforte's face and began asking questions. She stated that Jacobs, however, showed no sign of physical aggression and did not physically engage Gianforte before being attacked by the Republican candidate.
On June 12, following the election, Gianforte was sentenced to community service and fined $385 after admitting the charge.
Endorsements.
 ;templatestyles src="Endorsements box/styles.css"/ ;Greg Gianforte
Statewide officeholders
Local officeholders
Individuals
Organizations
Newspapers
 ;templatestyles src="Endorsements box/styles.css"/ ;Rob Quist
U.S. senators
Governors
Local politicians
Individuals
Labor unions
Organizations
Websites
 ;templatestyles src="Endorsements box/styles.css"/ ;Mark Wicks
Local officeholders
References.
 ;templatestyles src="Reflist/styles.css" / ;
External links.
Official campaign websites