Former Montana Lt. Gov. John Bohlinger (D) will run for his state's open Senate seat, creating a potentially competitive primary that could complicate Democrats' chances of holding onto the seat.
Bohlinger, a former Republican who served with former Montana Gov. Brian Schweitzer (D), has filed papers with the FEC to run as a Democrat.
Sen. Jon Tester (D-Mont.) endorsed Walsh on Wednesday, calling the military veteran "a leader who puts service over self — who always puts Montana and Montanans first."
Rep. Steve Daines (R-Mont.) is expected to announce his own bid later on Wednesday, and will likely begin the race with an edge in the GOP-leaning state.