The Washington PostDemocracy Dies in Darkness

How contested House districts shifted from 2016 to 2018

The U.S. Capitol, the morning after Election Day, as Democrats take back the House. (J. Scott Applewhite/AP)

To the frustration of people who enjoy neatness, considering one election in relation to another is never as clean as one might like. We tend to think of elections as broad indicators of how the electorate is moving nationally, but the electorate, always unwilling to conform to predicted boundaries, tends to swirl into eddies and reverse direction in ways that blur neatly drawn lines.

For example.

Let’s evaluate this week’s House races against a common standard: how each district voted in the 2016 presidential election. Comparing the margin between the Democrat and the Republican in House races with the margin between President Trump and Hillary Clinton is about as good a universal metric as we have, indicating how districts changed over the past two years.

It’s perhaps obvious that the country broadly moved back to the left after 2016, given that the Democratic Party regained control of the House. But a map of the shifts in contested House races makes clear how broad that shift was.

The size of the squares above correlates to the size of the shift to one party or the other. Blue is a shift toward Democrats; red, to Republicans.

As of writing — early on the morning after the election took place — House districts shifted to the left by a 3-to-1 margin: About 300 moved left and 100 moved right. There are scattered exceptions in the Midwest and the South, and two solid pockets of shifts worth noting.

The first is south Florida, where several Republican House candidates did a bit better than Trump did two years ago. That doesn’t mean the Republican won; one such district is Florida’s 26th, which the Democrats picked up. Clinton won the district by a wide margin; the Republican incumbent, Rep. Carlos Curbelo (R), lost it more narrowly. A shift to the right, explained in part by the specific circumstances.

The other pocket is California, where similar dynamics occurred in a number of races. But there’s an important additional factor there: Much of the vote still remains to be counted, thanks to the state’s generous voting system, which also takes a long time to complete. Take those numbers with something of a grain of salt.

Where the country got more Democratic is perhaps more interesting. Notice Michigan, Iowa, Minnesota — the Midwest, generally. This was the region that gave Trump the presidency, thanks to narrow margins in Michigan and Wisconsin in particular. In the three states that gave Trump the 78,000 votes that won him the electoral vote, there were 38 contested House races. Democrats improved on Clinton’s performance in 28 of them.

There’s a caveat to the map above. The Trump-Clinton contest was a very specific race between two particular people. If there were places where Clinton was a particularly unpopular candidate, for example, we might expect to see the district shift to the left if voters were given an opportunity to vote for just about any other Democrat.

So let’s compare the 2018 results with 2012.

Here we get a better sense for how the country has changed. The Midwest, and Ohio in particular, voted much more heavily Republican in 2018 than six years ago. So did much of Florida (which Barack Obama won in 2012), the Central Valley of California and parts of the New York-Philadelphia corridor in the northeast.

Overall, more districts shifted to vote more Democratic than shifted to vote more Republican, though by a more modest margin than the change from 2016 to 2018.

Two states in particular stand out in that regard. The first is Utah, where Mitt Romney did particularly well in 2012. (And in 2018; he was just elected that state’s senator.) The other is Texas, where a combination of a shifting electorate and the insurgent campaign of Rep. Beto O’Rourke (D) spurred a surge in Democratic votes in the state this year.

As in juxtaposing with 2016, though, comparing 2018 results to 2012 means comparing individual races to an election between two particular candidates (as we see with those Utah results).

So we speak in broad terms: The country got more Democratic in 2018, even in places where Trump showed unexpected strength in 2016.