Rep. Steve Daines (R-Mont.) will announce his Senate bid next week, sources tell The Hill.
Daines, a freshman congressman, has long been expected to run for the seat.
"We fully expect him to announce his intentions about the Senate race on Wednesday," said one Montana Republican with knowledge of Daines's plans. "It is very likely that he'll be announcing his Senate bid."
Daines is holding a "special event" in his hometown of Bozeman on Nov. 6 to "thank supporters," according to an invitation to the event obtained by The Hill.
He has long been expected to run for the Senate and recently told The Hill that he would make a decision on the race by the end of the year.
Daines's spokeswoman wouldn't say if the event would include a Senate announcement.
"This is an event to thank Montanans who have been there to support Steve and his fight to change Washington," said Daines spokeswoman ALee Lockman.
Incumbent Sen. Max Baucus (D-Mont.) is retiring, and Daines is likely to face Montana Lieutenant Gov. John Walsh (D) in the general election. Republicans are bullish about their chances with the freshman congressman in the GOP-leaning state.