As of this writing, we’ve had 18 standard D vs. R special elections in 2018, and the results couldn’t be more clear. Democrats have flipped 6 out of 16 Republican-held districts, and outperformed Hillary Clinton’s margin in all except one. And in that one, Connecticut’s House district 120, Democrat Phil Young won anyways, picking up a seat held by Republicans for the past 44 years and outperforming previous Democrats running for that seat by double-digit margins—not exactly something for Republicans to find comfort in.
Let’s take a graphical tour of the results!
On average, Democrats have outperformed Clinton’s margin by 25 points in 2018.
Democrats have also outperformed Barack Obama’s 2012 margin by 13 points on average.
Another way to look at these data is to plot the margin of the specials against the presidential margin. Points above the diagonal line show where the Democrat outperformed Clinton or Obama in the special election:
Compare to the 2017 special elections:
This year seems to be even better for Democrats so far, although the regions where Democrats underperformed in 2017 (Washington, Florida’s heavily Cuban districts, and parts of the Northeast, for the most part) have not had many special elections yet in 2018. Still, there’s a clear contrast when you look at the same graphs for the 2014 special elections:
Speaking of geography, here’s the change from the 2016 presidential margin in map form, for the entire 2016-2017 cycle. Note this is the margin change, not the specials margin. There’s certainly geographic patterns. The difference between state and national parties is part of it; the party of the current governor may also be a factor.
And here’s the map for the comparison to Obama’s margins:
And one last map: locations of all the seats that have been flipped since November 2016, including seats that aren’t standard D vs. R elections, the Alabama Senate seat, and regularly scheduled elections in New Jersey and Virginia.
What about comparing results to previous elections for the same position in the same district? You can see those margins in green at the figure at the very top of this post. Comparing to prior legislative elections lets us look back much further in time. For each year, a special elections index can be computed that allows for us to measure the electoral environment. (For a detailed explanation, see this post.)
The biennial index, which calculates just one value for each election cycle, is still pretty stable, and clearly much higher than 2008.
This matters because the special elections index is correlated with the House popular vote. The special elections results are, as a whole, very good news for Democrats.