You can’t predict outcomes this far out, but these hard facts scare the hell out of Republicans:
Eight House GOP chairs have retired: You don’t climb to the top of power in Congress and leave unless you feel confident your reign will soon end. (Another factor: Chairmanships are term-limited from a Gingrich-era reform.)
Record retirements for GOP: Already, 29 GOP seats are open, a pace far exceeding the past two elections that saw power change hands.
Democrats outperformed their norms in turnout, and in total votes, in all seven 2017 elections. This is a clear indicator of energy.