FiveThirtyEight

Things are about to get exciting again for election junkies. Next week, we’ll be treated to the first congressional election since December’s contest for one of Alabama’s U.S. Senate seats: a special election in Pennsylvania’s 18th Congressional District. And another Democratic upset could be in the works: Polls show a tight race in this very Trumpy district that includes Pittsburgh ’burbs and rural areas in the southwestern corner of the state.

Special election results so far this cycle are among the clearest portents of a Democratic wave in November. Democrats are beating their usual percentages of the vote not only in special federal elections (i.e., for the U.S. Senate and House), but also in special state legislative elections. All told, after a trio of legislative specials last Tuesday, there have now been 127 special elections in 28 states since President Trump’s inauguration on Jan. 20, 2017. In the 95 of those races to pit at least one Democrat against at least one Republican, Democrats have outperformed the normal partisan lean of their districts by an average of 13.2 percentage points.

But a wave may not crash uniformly on every shore. As state-by-state polling of Trump’s approval rating shows, the national mood really isn’t so national. Voters in different corners of the country differ in how deep their anger runs — and at whom it’s directed. This could have big implications for the midterm elections, considering how important political geography is these days. An inefficient distribution of Democratic support could (and has in the past) severely curtail the party’s prospects for gains. (For example, according to some simulations, Democrats could win the House popular vote by double digits and still lose the chamber because of Republican advantages in how the districts are drawn. And to take control of the Senate, it doesn’t much matter how Democrats perform elsewhere if they can’t win both Nevada and Arizona and defend red-state Democrats in places like Missouri and Indiana.)

Luckily for us, those regional variations are reflected in special election results. We broke down those 95 special elections by state to see where Democrats are exceeding expectations by the biggest margins — and where Republicans are holding their own. Here’s what we found:

How Democrats have fared in special elections

Difference between Democratic vote margins in each state’s special elections vs. those districts’ partisan leans,* since Jan. 20, 2017

*A district’s “partisan lean” is the average difference between how the district voted and how the country voted overall in the last two presidential elections, with 2016 weighted 75 percent and 2012 weighted 25 percent.

Source: Ballotpedia, secretaries of state, Daily Kos Elections, Matthew Isbell

Now, we urge you to take plenty of caution when interpreting these results. They carry a lot of uncertainty — even more than is normally called for when extrapolating special elections to general elections — because the sample size for individual states is so much smaller. Think about how a poll’s margin of error is bigger for subsets of the overall sample; it’s the same principle.

We know from past experience that a single special election isn’t a very accurate guide to future results; only when you average them together do they acquire their predictive power. That’s because individual elections can turn on any number of race-specific factors, such as candidate quality or local idiosyncrasies. We strongly advise paying more attention in the table above to the states that have multiple data points.

Even states with two results can be skewed by one weird race. Kentucky, which ranks No. 1 in swing toward Democrats, is a great example. Local Democrats in Kentucky aren’t viewed the same as federal Democrats: Despite voting for Trump 63 percent to 33 percent, the Bluegrass State still has a Democratic attorney general and secretary of state, and Democrats controlled the state House from 1921 to 2017. In other words, it’s not a new development for a legislative Democrat in Kentucky to dramatically outperform Barack Obama and Hillary Clinton. In addition, half of Kentucky’s 56.9-point Democratic surge can be attributed to last month’s highly unusual race for Kentucky House District 49. The seat’s Republican incumbent killed himself after being accused of sexually molesting a teenager, and his widow ran for the seat on the platform that the allegations were a liberal smear campaign. She got crushed, 68 to 32 percent, by the seat’s last Democratic occupant. Only a fraction of the 84-point (!) Democratic swing in that race can probably be chalked up to anti-Trump enthusiasm.

But the Democratic overperformance in other states is harder to dismiss. With a relatively robust sample of eight elections, Oklahoma is No. 2 on the list — Democrats have beaten the partisan lean there by 32.1 points, on average. That may seem surprising in such a red state, but it makes plenty of sense when you consider Republican Gov. Mary Fallin’s horrid 61 percent disapproval rating. Gubernatorial popularity may explain what we see in other states as well. For example, in Connecticut, it is actually Republicans who have outperformed in special elections, by an average of 5 percentage points. That could be because Democratic Gov. Dan Malloy is the least popular sitting governor in the country. And Republicans are beating the partisan lean by an average of 1.2 points in Massachusetts, where Republican Charlie Baker is America’s most popular governor.

One pattern that should worry Republicans is that Democrats appear to be running farthest ahead of their presidential candidates in red states. The top nine states on the list all voted for Trump in 2016, while eight of the bottom 12 voted for Clinton. That suggests that Democrats are indeed doing better in the conservative areas where they need to make 2018 inroads. Specifically, special election results suggest that the white-working-class-heavy Midwest — which broke heavily for Trump in 2016 — may not be lost for Democrats after all. Democrats’ 26.2-point overperformance in Iowa, for instance, may help Democrats pick off two House seats they would probably need for the House majority.

And, as I mentioned, Democrats will have to defend several Senate seats in ruby-red states to have any chance of winning that chamber; these numbers should give them hope. The 21-point Democratic overperformance in Missouri, for example, should bolster the confidence of Sen. Claire McCaskill, one of the Democrats’ most endangered Senate incumbents.

It’s not all bad news for Republicans. Florida, a crucial swing state this and every year, ranks 26th in Democrats’ relative performance — dead last. As in Kentucky, part of this can be explained by differences between presidential and local elections — two Miami special elections took place in heavily Cuban-American communities that rejected Trump but still vote Republican down-ballot — but that just underlines the fact that races like those for Florida’s 26th and 27th congressional districts may be heavier lifts for Democrats than their presidential numbers suggest. Georgia is another state where Democrats have high hopes to score a win or two but where Republicans have outperformed in special elections by 2.6 points, suggesting they will do no worse than Trump did in the Peach State.

Finally, Republicans bested their previous marks in Washington special elections by 6.4 points, making it their third-best state. This one is harder to explain, but it may have to do with the way Washington holds its elections. Part of the reason that Democrats have outperformed in so many special elections is that Democrats seem more motivated to vote, leading to wide turnout disparities between Democrats and Republicans. Washington, though, conducts elections entirely by mail, which means turnout there is consistently high. Washington could therefore be a cautionary tale that a Democratic wave could dissipate — or even reverse itself — if Republicans end up turning out at rates similar to Democrats in the fall.

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