Quote (ThatAlex @ 6 Nov 2018 14:36)
Based on RCP projections:
House: D+27
Senate: R+2
Governor: D+7
That Governor number is really surprising. Republicans have been really effective in state races across the country for a while now. Will be curious to see how that shakes out. But of course, Congress takes center stage tonight, and deservedly so. I predict Republicans to do better than the projections and polling.
House: D+_7, not +27.

And most experts predict that, due to gerrymandering and self-sorting, the break-even point where the race for control of the House is a 50:50 toss-up lies somewhere between D+5 and D+7.
So in this sense, the GOP only needs a tiny polling error in their favor to be on even footing.
Due to the way the House is set up, going from a national average of D+5 to D+9 means odds going from 40:60 to 85:15 or so. This is the fun zone, where every tiny fraction of a percentage matters.
The Dems will do well on the governors races though. Gillum winning in Florida would be particularly huge, since he vowed to reinstate voting rights for felons who served their time - this could have a big effect for 2020 and push Florida out of the GOP's reach in a close national environment.