In Montana, Republican Tim Sheehy Tries to Outrun Jon Tester, and Scrutiny

Tim Sheehy, the novice Republican candidate in perhaps the most important Senate race in the country, was not downplaying his lack of a political pedigree when he stepped in front of a welcoming audience at the American Legion hall in downtown Big Timber, Mont.

“I’ve never been involved in politics,” he told the crowd of about 75 gathered for a recent stop in this ranching and mining community at the foot of the Crazy Mountains in sparsely populated Sweet Grass County. “It’s my first time running for anything. I’ve never run for student council.”

He is starting at the top in this crucial showdown with Senator Jon Tester, the three-term Democrat who finds himself the underdog in his changing home state in a contest that could decide which party holds the Senate majority no matter who wins the presidency.

“This race is not just an everyday Senate race,” Mr. Sheehy told his listeners, most of them older, with the men sporting Stetsons and trucker hats, their horse trailers and cattle trucks lined up outside. “This is not just whether you like old dirt farmer Jon Tester or not. This race determines control of the U.S. Senate. It’s that simple.”

It is true that given Democrats’ 51-to-49 majority and the almost certain Republican pickup of a West Virginia seat after Senator Joe Manchin III’s retirement, a win in Montana could very well hand the G.O.P. control of the chamber. But Montana’s Senate race has been anything but simple.

Senator Jon Tester, a third-generation Montana farmer and Democrat, is running for his fourth term in the Senate.Credit…Janie Osborne for The New York Times