Briefly on the Virginia and New Jersey Elections:
The results of those election can be subject to mistakes on both sides meaning they can be over thought or under thought.
To over think would be to see it as an inevitable harbinger of either 2020 or 2018. Case in point: 2009 did not mean Obama was toast in 2012 and the resistance folks in 2017 should remember that the tea party of 2009 was a lot less robust in 2012. As for the 2010 comparison to 2018, its way too early and folks forget: the backlash of 2010 was because of political overreach by the Dems. The GOP has not overreached yet, heck it debatable if they have even reached at all yet. Either way, the whiter and hotter the populism of a moment, the shorter its political shelf life tends to be.
As far as under thinking, to dismiss these results as just the results of blue states and thus presume it has no bearing whatsoever on 2018 (or does not reflect on a lack of coattails thus far for Trump) would be a mistake that could lead to a political complacency that results in a correction midterm election rather than an election where GOP can build on their advantages nationwide.
In short, its possible to overthink as well as underthink last night's results for the GOP as well as for the Dems.