Today’s political landscape is often dismissed as a partisan deadlock in which the vast majority of voters have already made up their minds and will only dig their feet in further with each passing news cycle. And the data speaks for itself: People seemed to choose party over candidate in 2018, and districts largely voted as expected, based on their previous voting habits and the national environment. Democrats won the House national popular vote by about 8.5 points and the margin in the two-party vote for House swung, on average, about 5 points toward Democrats, a continuation of a leftward swing that started in 2016.
But when you focus on how predictably Republican or Democratic a district is, you may miss the fact that a district’s partisanship can — and does — change over time. CONT.
Rachael Dottle & Galen Druke, FiveThirtyEight