Demographics, Turnout, and the Vote for the House

David Wasserman writes at FiveThirtyEight:

When the 114th Congress is sworn in on Jan. 3, House Republicans will boast their largest majority since Herbert Hoover was president. If all leaders in the yet-to-be-called races hold their leads, Republicans will go from 234 seats to 247, a triumph that exceeds their “Drive to 245” goal. Not even Republicans anticipated they were in for such a good year.

So how did they beat the point spread? The answer lies less in what Republicans did, and more in what Democratic voters didn’t do: show up to vote in so-called orphan states.

To ease my post-election withdrawal, I built a spreadsheet of results in all 435 districts to analyze what happened. What it illustrated: By winning just 52 percent of votes cast for the House, Republicans were able to win 57 percent of all House seats. Thanks in part to favorable redistricting after the 2010 Census, Republicans will likely have won five more seats than they did in 2010, even though Republican candidates won by less of an aggregate vote margin than they did four years ago.1

The election of a historically large Republican majority coincided with thelowest turnout in a midterm election since 1942. But the 2014 race for the House played out in two very different sets of states. In the 24 states hosting high-profile, competitive Senate or gubernatorial races, raw votes cast in House races were down an average of 30.5 percent from 2012.2 But in the 26 states that weren’t, raw votes were down a much more severe 43.9 percent.3

Sean Trende writes at RealClearPolitics:

The major difference was that in 2012 Barack Obama was a moderately popular president. In 2014, he is an unpopular president. If this does not change between now and 2016, demographic shifts alone will not save the Democratic nominee.

We can illustrate this best by borrowing a page from Harry Enten, and seeing what would have happened if the 2014 electorate had instead more closely resembled the 2012 electorate. That is to say, let’s keep whites voting 60-38 for Republicans, Hispanics voting 62-36 for Democrats, and so forth, as they all did in 2014, but alter their shares of the electorate to resemble 2012 (72 percent white, 10 percent Hispanic, and so forth) rather than 2014 (75 percent white, 8 percent Hispanic, and so forth). This allows us to isolate the effects of demographic change between 2012 and 2014.

The results are underwhelming: If the 2014 electorate had resembled the 2012 electorate in terms of race, the Republican vote share would shrink by just 1.97 percentage points. In other words, in a 2012 electorate, Republicans would have won the popular vote for the House by 4.5 points, rather than 6.5 points. That’s not nothing, as they say, but it still only explains a relatively small share of the difference between the 2012 and 2014 results. Put differently, if Obama had put up the same vote shares among racial groups in 2012 as Democrats ultimately did in 2014, he’d have lost.