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. As of 2025, this is the last time Democrats won a congressional and/or statewide election in Montana.
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.
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.
Kelly won the Green Party nomination, but a Montana district court judge ruled that he had insufficient signatures to get on the ballot.
From Secretary of State of Montana
Counties that flipped from Democratic to Republican
Official campaign websites