The AZ win is a pretty big deal, as is Montana, IMO. Several reliably red states go blue (or stay blue in the cases of MT and WV), but no blue states go red. That doesn’t bode well for the GOP’s chances in 2020.
A good economy might not be enough to keep them in the WH. If they could hammer out an immigration deal of some kind, that might give them the boost they need. They still have the health care issue to grapple with though, and I think that issue is an even bigger liability for them than Trump’s endless theatrics.
In any case, the Democrats may have fell short of expectations, but the momentum is clearly in their favor right now.