Rep. Matt Rosendale (R-MT) is eyeing a Montana Senate launch right before the March filing deadline, a move national Republicans fret could jeopardize a winnable seat.

According to a source with direct knowledge and four sources familiar with the matter, Rosendale has told colleagues he plans to launch his campaign shortly before the March 11 candidate filing deadline. One of the sources said that they believe Rosendale could launch as soon as the last two weeks of February. This would change the outlook on the race as Senate Republicans already have their preferred candidate, Tim Sheehy, and view Rosendale as a liability, as he has already lost to Sen. Jon Tester (D-MT) once before.