One of the many things missed in all of this is the role of regions in the midterm elections. For example, the "urban versus rural" narrative ignores just how different many rural regions are from each other. You can see this in the election results. Iowa has long had a progressive rural block in its eastern counties, and this year the Democrats flipped two seats in that state.
More broadly, the Midwest went hard for the Democrats. This region was mostly ignored in the pre-election coverage in favor of Georgia, Texas, and Florida, so reporters missed a huge story. No other region probably suffered more under the Tea Party policies and governors of the early to mid-2010s. This election was a huge rebuke, with Tea Party poster child Scott Walker sent packing in Wisconsin, Bruce Rauner canned in Illinois, Michigan brought back to the fold, and Kansas flipped after years of the Brownback disaster. I see a similar dynamic in New Jersey, which endured eight years of Chris Christie. This state will now be represented by Democrats in eleven of twelves of its districts. States that had been put under the yoke of activist conservative governors have proven to be receptive to the Democrats.
Trump and the Republicans put all their chips on an anti-immigrant, white nationalist appeal. While those arguments sadly appeal to white people nationwide, they appeal most to white people living in the South. You can see this in the election results. The South mostly held for Republicans, but pretty much all of the other regions did not. The current iteration of the Republican Party is such that it alienates a lot of "purple" suburbs, which is easy to see in the election results in New Jersey, California, and Virginia. Heck, the Republicans lost a seat that includes Cobb County, Georgia. That was once Gingrich country.
The Republican strategy of firing up the base and everyone else be damned appears to be running into trouble. The Bible-thumping part of the base is weak on the coasts. In fact, it alienates swing voters in those places. The low-tax Republican economic message used to appeal to suburban voters in places like New Jersey, but the abject failure of those policies on the state level has discredited them.
If the Democrats are able to maintain their new hold on the Midwest and their increased margin of victory on the coasts, 2020 will be in the bag. Here's hoping that this regional shift holds.