House seats vacated by Republicans but carried by Clinton will be nearly impossible for the party to maintain:
With the retirement announcement of Pennsylvania Republican Rep. Ryan Costello, there are now eight open seats currently held by Republicans in districts that Hillary Clinton won in 2016.
And there’s a good chance the Democrats will win them all, bringing the party 35% closer to the 23 seats it needs to flip to win control of the House.
That’s because the opposition party just doesn’t lose seats like these eight in midterm elections.
Going back to 1994, the president’s party is batting 0.000 in seats like Costello’s, where there will be no incumbent on the ballot and where the president’s party’s candidate won in the previous House election but the opposition party’s presidential candidate won in the previous presidential election. (Hat tip to the Cook Political Report’s Dave Wasserman, who first pointed out this statistic.)
The factors that lead to a wave tend to be self-reinforcing. For some reason, the out party in midterm elections always seems to have better messaging…