This was probably the Republicans' last chance to win anything statewide in VA. Barring a Larry Hogan vs. Anthony Brown situation, Ds should have a lock on the state and things will only get worse for the VA GOP from now on.
To me it looks more like VA is completely inelastic with a built in Dem edge since 2010. 3-6% Dem edge in presidential years, no matter what, and a 1-3% Dem edge in off-years and midterms.
However, if Gillespie does win on Tuesday, as he has about a 40% chance of doing, I think we have to give Trump VA if he wins the PV in 2020. So I wouldn't say this is the last chance, but 2020 likely will be.
I now think Fairfax and Herring will both outrun Northam and that Northam will trail the legislative generic ballot. So a Gillespie + 0.5% win with all other statewide Dems winning and a bunch of Dem HoD gains is a distinct possibility. I don't know how the heck I would interpret that in terms of 2018/20.
Really don't see it. Trump is beyond toxic in VA, and the state already voted 4 points to the left of the nation in 2016. Trump has little room for growth in the rural areas, but NoVA, Virginia Beach, Richmond+suburbs, etc. are far from maxed out for Ds. With the way Trump has governed I really see no path for him to win there in 2020 (or any other Republican, btw).
Keep in mind that Kaine is from VA. Without Kaine, I think Clinton finishes somewhere between McAuliffe 2013 and Obama 2012. It would still vote left of the nation, but not as dramatically.
VP boost has historically given 2 points at a maximum to the home state. So at a minimum, this would put VA at 2 points left of the nation, compared to 2012 where it was pretty much exactly the same as the nation.
Also, here are the regions from the polls sampling that I posted above:
