Yes. The path to Dems holding the Senate is relatively narrow, but it certainly exists. Masters, Walker and Oz are all extremely flawed candidates who could definitely lose in spite of the environment.
Even Ron Johnson's favorability has massively declined since his last race. I suppose I'd still call him a narrow favorite, but him running probably makes the race harder for the GOP than it needs to be.
I agree.
If Ron Johnson chose not to run again, it's likely that Mike Gallagher or Bryan Steil ran.
In that situation, Democrats would have less of a shot in Wisconsin.
While incumbency is usually a good thing, Ron Johnson is an exception given how much he's gone off the rails.