Nov. 8, 2018: U.S. Sen. Jon Tester, Montana Democrat, was re-elected to office on Tuesday, Nov. 6, 2018. Tester, 62, defeated Matt Rosendale, 58, Republican, the Montana State Auditor. With 91 percent of voting precincts reporting results, Tester led Rosendale by just more than 4,000 votes, reported The Associated Press. Tester is a two-term incumbent. Tester is a lifelong resident of Montana, and a farmer.