It will be the least shocking news ever if the only lesson Republicans take away from Tester's victory is that any Republican candidate who doesn’t have a Baltimore accent and has "incumbency advantage" will automatically be heavily favored even against the most popular statewide elected official (Bullock is more popular than Tester), and they inevitably blow it again in 2020 even if Trump wins reelection. Yeah, we get it, Rosendale wasn’t a strong candidate, it’s true, but it’s silly and absolutely lazy to lay all the blame for Tester's victory on him. Even many Republicans have already admitted that the late and half-hearted NRSC involvement in Montana was the most decisive factor in his defeat, and the Democrats' ground operation (particularly on college campuses and reservations) shouldn’t be underestimated. There’s zero reason to believe that Democratic base voters aren’t going to turn out in 2020 or that they will be more supportive of Daines than Rosendale.
I maintain that this seat is more likely to flip than Iowa, even if Bullock declines to run for some reason (which would hardly make the race Safe R). Daines is absurdly overrated on this forum and among pundits in general and very beatable if Democrats play their cards right and/or 2020 is a favorable year for Democrats.
another reason republicans keep loosing are also Libertarians voting against there own interest.