I had been thinking of writing something like this piece by Matt Yglesias, but he seems to have bounced back faster and said it better. It is true that Democrats do work in mid-term elections, the house appears to be very effectively gerrymandered, and the senate tends to be in defense for the Democrats in the mid-term years (as they have to defend gains made at a presidential cycle).
It's also not good to hear that:
The GOP now controls historical record number of governors’ mansions, including a majority of New England governorships.So what next? I think Democrats should consider trying to compete at all levels. After all, states are where the gerrymander is executed and there is no reason not to start thinking about how to win some of them. The 2020 census is closer than it may look. The presidency is important, but it may have left the party complacent about the rest of the political process.