The Southern White Vote in Congressional Elections

It is now much harder for Democrats to win House elections in the South. Harry Enten writes at FiveThirtyEight:

We can see the abatement of white Southern Democrats in the Cooperative Congressional Election Study (CCES) data set. The poll, which started in 2005, surveys over 50,000 people nationwide every two years, providing more accurate demographic and geographic subgroup data than other publicly available surveys. The CCES also verifies the voting status of all its respondents to see if they’re registered.

In the 2006 House elections, Republicans won Southern1 white voters by 16 percentage points, 58 percent to 41 percent,x

Due to rounding, margins may be different than one would find by subtracting the percentages of the vote that individual candidates received.according to the CCES.3 

That may seem like a wide margin, but Democrats did well enough with white Southerners to win in several majority-white districts. Democrats like Lincoln Davis and John Tanner won in Tennessee. The majority of Arkansas’s delegation was Democratic.
Of course, 2006 was also a very good year for Democrats; they won the national House vote by 8 percentage points. So as our baseline, let’s look at how Republican-leaning the Southern white vote was relative to the national House vote. In 2006, Republicans lost the national House vote by 8 percentage points but won white Southerners by 16 points. The relative difference gives us the lean — white voters in the South were 24 percentage points more Republican-leaning than the country that year.

The 2014 election (the last for which we have CCES data) was a much different story. Southern whites voted Republican 70 percent to 28 percent4— a margin of over 40 percentage points, more than double the GOP’s margin among white Southerners in 2006. Once you take into account the fact that Republicans won the national House vote by 6 points and that the overall CCES sample was slightly more Democratic than the actual vote, Southern whites were still 39 percentage points more Republican-leaning than the nation. That’s a 15 percentage point jump from 2006. To put that in perspective, people are making a big deal over some Midwestern states — Michigan, for example — going from slightly more Democratic than the nation to slightly more Republican between the 2012 and 2016 presidential elections. What’s occurred in the House over the past decade is a political earthquake by comparison.