2018 United States Senate election in Montana

The 2018 United States Senate election in Montana was held on November 6, 2018, to elect a member of the United States Senate to represent the State of Montana, concurrently with other elections to the United States Senate, elections to the United States House of Representatives and various state and local elections.

This was one of ten Democratic-held Senate seats up for election in a state that Donald Trump won in the 2016 presidential election. Incumbent Democratic Senator Jon Tester was reelected to a third term, defeating Republican State Auditor Matt Rosendale. Rosendale conceded on November 7, 2018. This was the first Senate election in which Tester received a majority of votes cast rather than a simple plurality.

Following his loss, Rosendale went on to run for Montana's vacant congressional seat in 2020 and won, taking office in the U.S. House of Representatives in January 2021.

Nominated

 * Jon Tester, incumbent U.S. Senator

Nominated

 * Matt Rosendale, Auditor of Montana and candidate for Congress in 2014

Eliminated in primary

 * Troy Downing, veteran and businessman
 * Russell Fagg, former Yellowstone County District Judge
 * Albert Olszewski, state senator and candidate for lieutenant governor in 2012

Withdrew

 * Ron Murray, businessman and candidate for the state house in 2010

Declined

 * Tim Fox, Attorney General of Montana
 * Robert J. O'Neill, former Navy SEAL (endorsed Troy Downing)
 * Marc Racicot, former governor and former chairman of the Republican National Committee (endorsed Russell Fagg)
 * Corey Stapleton, Secretary of State of Montana, candidate for governor in 2012 and candidate for Congress in 2014
 * Ryan Zinke, former Secretary of the Interior and former U.S. Representative

Results
[[File:2018 MT US Senate Republican primary.svg|thumb|Results by county Map legend

{{legend|#c83737|Rosendale—60–70%}}

{{legend|#d35f5f|Rosendale—50–60%}}

{{legend|#de8787|Rosendale—40–50%}}

{{legend|#e9afaf|Rosendale—30–40%}}

{{legend|#f4d7d7|Rosendale—<30%}}

{{legend|#cccccc|Rosendale/Fagg tie—30–40%}}

{{legend|#afe9af|Fagg—30–40%}}

{{legend|#87de87|Fagg—40–50%}}

{{legend|#5fd35f|Fagg—50–60%}}

{{legend|#afdde9|Olszewski—30–40%}}

{{legend|#87cdde|Olszewski—40–50%}} ]]

Nominated

 * Rick Breckenridge, 2016 candidate for the U.S. House of Representatives

In October 2018, Breckenridge told a reporter from the Associated Press that he opposed the use of dark money in politics. Breckenridge said that he realistically anticipated only receiving three or four percent of the vote in the general election, and that he endorsed Rosendale's efforts to stop the use of dark money in politics. The Associated Press interpreted Breckenridge's comments as a statement that Breckenridge was dropping out of the race and endorsing Rosendale. Breckenridge later stated that his use of the word "endorse" referred only to stopping the use of dark money in politics, and said he was still running for the Senate.

Green Party
Kelly won the Green Party nomination, but a Montana district court judge ruled that he had insufficient signatures to get on the ballot.

Nominee (removed from ballot)

 * Steve Kelly, artist and environmental activist

Eliminated in primary

 * Timothy Adams

Results
[[File:2018 MT US Senate Green primary.svg|thumb|Results by county Map legend

{{legend|#0b2817|Kelly—100%}}

{{legend|#16502d|Kelly—≥90%}}

{{legend|#217844|Kelly—80–90%}}

{{legend|#2ca05a|Kelly—70–80%}}

{{legend|#37c871|Kelly—60–70%}}

{{legend|#5fd38d|Kelly—50–60%}}

{{legend|#87deaa|Kelly—40–50%}}

{{legend|#cccccc|Kelly/Adams tie—30–40%}}

{{legend|#999999|Kelly/Adams tie—50%}}

{{legend|#d35fbc|Adams—50–60%}}

{{legend|#c837ab|Adams—60–70%}}

{{legend|#280b22|Adams—100%}}

{{legend|#000000|No votes}} ]]

Debates

 * Complete video of debate, C-SPAN September 29, 2018
 * Complete video of debate, YouTube October 14, 2018

Results
[[File:2018 MT Senate swing by county margins.svg|300px|thumb|Swing by county Legend

{{legend|#77e3ff|Democratic—+10-15%}}

{{legend|#AAEEFF|Democratic—+5-10%}}

{{legend|#D5F6FF|Democratic—+<5%}}

{{legend|#FFD5D5|Republican—+<5%}}

{{legend|#FFAAAA|Republican—+5-10%}}

{{legend|#FF8080|Republican—+10-15%}}

{{legend|#FF5555|Republican—+15-20%}}

{{legend|#FF2A2A|Republican—+20-25%}}]]



By county
From Secretary of State of Montana


 * Counties that flipped from Democratic to Republican
 * Chouteau (largest municipality: Fort Benton)
 * Rosebud (largest municipality: Colstrip)
 * Yellowstone (largest municipality: Billings)