A look at the electoral map for 2016 shows that today’s democrat is most likely a city dweller, leaving rural districts to republicans. This means most democrat politicians are going to take policy positions that appeal to urbanites and most likely further divide this nation along political lines.
See the 3D map that starkly shows the difference of where the two parties dwell, Here
Nat Silver’s FiveThirtyEight speculates that it would take a huge backlash against the Republicans for the Democrats to ever win back control of the Senate, much less the House. Here