This is obvious to anyone who has paid attention to mid-term elections in this country. At the end of the day, they are driven by the presidents performance. Republicans are fooling themselves if they think hyper partisanship and gerrymandering will protect them from a Trump backlash.
If the GOP was more controlled and didn't have a President with such a garbage approval rating, than these two factors plus geography could save their majorities. 538 calculated that the Demcorats have to win the PV by an entire 8 points in order to take back the House. That's the price gerrymandering and polarization come with.
As it stands the Democrats are currently projected to win the PV by 8-9 points so they're in a good position.
