Democrats picked up their first state legislature seat in 2018 on Tuesday, as the party’s candidate won a special election for a state Senate seat in Wisconsin’s 10th District.

Though Donald Trump had won the rural district by about 17 points in the 2016 presidential election, Democratic nominee Patty Schachtner defeated her Republican opponent for the open seat by a comfortable margin of about 10 points.

The news is setting off alarm bells for Republicans, who are increasingly worried about a Democratic wave in the 2018 midterms. Gov. Scott Walker, the conservative two-term Wisconsin Republican running for reelection again this year, openly tweeted about his concerns:

Senate District 10 special election win by a Democrat is a wake up call for Republicans in Wisconsin. — Scott Walker (@ScottWalker) January 17, 2018

And beyond the dynamics in this particular race, the bigger picture is that Democrats have been doing quite well, on average, in special elections for both state legislature and congressional seats across the country ever since Trump won.

It’s often said that “special elections are special,” and that’s certainly true. Each one takes place in a particular area with particular candidates, they’re usually low-turnout contests, and it’s a mistake to draw broad generalizations from any particular one.

The good thing about special elections, though, is that since there are a lot of them, you don’t have to generalize from just a few. According to data compiled by Daily Kos Elections, there have been 44 state house elections and 24 state Senate elections in which a Democrat and Republican nominee were pitted against each other since Trump won — in addition to the one US Senate and 5 US House elections of this nature that got much more national coverage.

And these results show us that on average, Democrats are doing much better than they did in the 2016 presidential race.

The parties’ performance in Trump-era special elections, by the numbers

The good folks at Daily Kos Elections have a spreadsheet for which they painstakingly compiled all the state legislature, congressional, or US Senate special election results in which a Democratic nominee and a Republican nominee ran against each other, and compared them to past years’ presidential results. And a look at the data on their spreadsheet tells us the following:

In the 74 special elections for both state legislatures and Congress across the country since Trump won that they tracked, Democrats performed, on average, 11 points better than they did in those areas in the 2016 presidential election.

While the average movement was in Democrats’ favor, there was a fair amount of variation. In 49 of those races, the Democratic candidate’s margin was better than Hillary Clinton’s in 2016. In 23 races, the Republican candidate did better than Trump. In the other two, it was about a tie.

Democrats aren’t just running up the score in already-blue areas. The party made many of its biggest improvements over the 2016 presidential in districts Trump won in the South and Midwest. This goes to show that the 2016 elections don’t at all seem to have heralded doom for Democrats in regions that tipped to Trump — in fact, it’s many Republican-held seats in those regions that suddenly seem to be flipping to Democrats for the first time in years.

Overall, 14 of those elections have resulted in a seat flipping from Republican to Democrat, compared to just a single one that flipped from Democrat to Republican (a state Senate seat in Massachusetts). The seats flipping to Democrats famously include the Alabama US Senate seat now occupied by Doug Jones, but also eight state house seats and 5 state Senate seats.

Of course, none of this even counts the regularly scheduled statewide elections in Virginia and New Jersey last November. In those, Democrats picked up on net 15 Virginia state house seats, 2 New Jersey state house seats, and one New Jersey state Senate seat, as well as the New Jersey governorship. This suggests the Democratic swing isn’t just a flukey dynamic of low-turnout special elections.

The numbers looks awful for Republicans. But they still have several months in which to turn things around.

Beyond election results, there’s other data that suggests a Democratic wave in 2018 is a strong possibility.

Still, Republicans do have some important points in their favor:

The Senate map is extraordinarily tough for Democrats — they’re defending 26 seats, and Republicans are defending just eight. Furthermore, many of the Senate Democrats on the ballot are in deep-red states that voted for Trump by double digits in 2016.

Republicans also have an advantage over Democrats in district maps for the US House and state legislatures across the country. This advantage is partly due to gerrymandering — the GOP’s 2010 midterm landslide let the party draw the lines in many states — and partly just due to where voters of different demographics have chosen to live. Either way, it could be an edge for the party in closely contested races.

Finally, there’s time. The election is still more than months away, after all, so news events and other political developments could still shift the environment in Republicans’ favor.

Of course, it’s also possible that news events in the coming months could move the race in Democrats’ favor. For instance, the economy could take a turn for the worse. There’s that high-profile investigation of the president and his associates, which will likely get some headlines this year.

We don’t know what the future will hold. But overall, the message from the 2017, and now early 2018, special election results should be quite troubling for Republicans. For now, the Democratic base appears remarkably energized. If they can keep it up until November, the real question will be just how big Democrats’ gains end up being.