The Republican defeat in New Jersey is unsurprising. The deep-blue state went for Hillary Clinton by 14 points, and on Tuesday the next governor, Democrat Phil Murphy, won by 13. The Republican nominee, Lt. Gov. Kim Guadagno, simply couldn’t escape the gravitational pull of her unpopular boss, Gov. Chris Christie, whose favorability in exit polls was a sad 22%.

The GOP’s loss in purple Virginia is far more problematic, with grave ramifications for the 2018 midterms. Mrs. Clinton carried the state by 5 points, but Democrat...