U.S. Senator Jon Tester meets with striking members of the International Boilermakers Union Local D239 and their supporters outside Imerys Talc America Inc. in Three Forks, Montana, U.S., October 13, 2018. REUTERS/Jim Urquhart/ File Photo

(Reuters) - Democrat Jon Tester, who has represented Montana in the U.S. Senate for more than a decade, overcame a tough election challenge from Republican Matt Rosendale to keep his seat, media outlets reported on Wednesday.