I don’t believe 17% of Democrats voting for Greg Gianforte for a second, but it’s Gravis so I shouldn’t expect much.
Their crosstabs can be very weird, I honestly wouldn’t pay any attention to them. But yeah, I know this forum is convinced that Montana is the most elaaaaaaaastic state in the country, but I’d be very surprised if Gianforte did 13 points better than Rosendale. Obviously there will be no shortage of Tester/Gianforte voters (and let’s be honest here: Williams' first name doesn’t help), but Gianforte, while not an extremely weak incumbent, isn’t exactly someone with a lot of crossover appeal, and I fail to see in which areas of the state he’s going to do much better than last time around. My current prediction is Tester +3, Gianforte +5/6, and I wouldn’t call either race "safe" for the incumbent (Lean D and R, respectively, is a fair rating at this point IMO).
Also, I’m not sure where this idea that Fox is the electoral savior of the MT Republican Party who will make MT-GOV 2020 Safe R comes from.