Already, Montana is of the most closely watched Senate races set for next year. Along with races in Arizona and West Virginia, the seat is one of a handful expected to determine control of the chamber’s majority in the next Congress.

Sheehy’s announcement also comes as Rep. Matt Rosendale (R-Mont.), who ran for the seat and lost in 2018, plots a second bid to unseat Tester, having told lawmakers that he plans to seek the GOP nomination. It’s unclear when Rosendale would make it official, but if he does, a crowded primary could complicate the party’s chances of retaking the Senate.

While deployed, Sheehy spent time in Iraq, Afghanistan, South America and the Pacific region, earning multiple combat decorations, including the Bronze Star and the Purple Heart. After returning to Montana, he founded Bridger Aerospace and its sister company, Ascent Vision Technologies, and he owns a cattle ranch for beef production.

National Republican Senatorial Committee Chair Steve Daines (R-Mont.) praised Sheehy’s decision but stopped short of an endorsement.

“Tim Sheehy is a decorated veteran, successful businessman, and a great Montanan. I could not be happier that he has decided to enter the Montana Senate race,” Daines said in a statement.