Turnout Data Reveals the Core of Democrats’ Success in Special Elections

Over the last year, two different sets of data have yielded two very different theories of where Democrats stand heading into 2024.

On one hand, there’s polling. Survey after survey shows President Biden even or trailing against Donald J. Trump. Voters, especially young and nonwhite voters, appear extremely dissatisfied with the president. No matter how good the economy looks to economists, most voters still say it’s bad.

On the other hand, there’s election results. Almost every time polls bring Democrats down, there’s a special election result to bring them back up. Special elections occur outside regular election cycles to fill a vacated seat, and overall Democrats have outperformed Mr. Biden’s 2020 results by four percentage points in these elections since the Supreme Court’s overturning of Roe v. Wade, according to data compiled by Daily Kos.

The limitations of polling are well known, especially one year before an election. The limitations of relying on special elections, on the other hand, are not as well understood. Unlike polls, special election results are hard facts, which make them tempting to view as a clear read into the 2024 electorate.

But special electorates bear no resemblance to the general electorate or the broader pool of registered voters, based on an analysis of voter registration records from more than 50 special elections since the start of 2022. They may offer insight into which party’s activist base is more energized, but not much more.

In the typical special election, half of voters are 65 and over. Nearly every special election voter has participated in a recent primary election. Almost everyone is a registered Democrat or Republican. Young voters, irregular voters and independent voters are much scarcer. The nonwhite share of voters is typically smaller. A general election poll with these demographic characteristics would be laughed out of the room.

As a result, special elections behave very differently from higher-turnout elections. They’re mostly decided by turnout, as the electorate consists almost entirely of the most partisan and least persuadable voters. At the same time, special election turnout is extremely volatile, with the ultralow turnout enabling turnout advantages that simply don’t happen in higher-turnout and regularly scheduled general elections.

The source of Democratic strength in specials over the last year, our analysis confirms, is therefore quite simple: It’s about turnout.

Biden voters have turned out at higher rates than Trump voters in special elections, according to estimates based on voter file data. This turnout edge explains the entirety of the Democratic performance overall. Even more convincingly, turnout explains the results district by district, with special election outcomes aligning with New York Times estimates for the number of Biden voters who showed up.

A similar analysis for the general election — or abortion referendums — looks very different. In those higher-turnout elections, turnout plays a smaller role. Not only is the turnout less volatile, but many persuadable voters join the electorate and sometimes cross over to vote for a different party or specific issue.

The same story is evident in Wisconsin, where The Times has conducted more than 7,000 interviews since 2019 and can dive deeper into lower-turnout electorates than elsewhere. Unlike most states, Wisconsin has off-year general elections, with much lower turnout than in midterms. These aren’t special elections, but they draw from the same pool of highly engaged, partisan and older voters. The Times data suggests that almost all of the Democratic success in these recent contests, like a key state Supreme Court election in April, was attributable to a sizable turnout advantage unlike anything in a federal general election.

One final piece of confirmation comes from Times/Siena polling. Since 2019, we’ve interviewed 1,800 respondents in districts with special elections, including 1,000 in districts with elections since the Dobbs decision. These interviews are heavily concentrated in a handful of states where we’ve done the most polling — there are only 17 races where we have at least 10 validated special election voters. But they nonetheless show that Mr. Biden won about six percentage points more support among validated special election voters in post-Dobbs elections than registrants overall in the same districts.

How is it possible for Democrats to have such a sizable turnout advantage? It’s not just demographics. Yes, college graduates make up an outsize share of special electorates — about 10 percentage points higher than registered voters overall, based on Times/Siena polling. But the Democratic edge runs much deeper. Across every demographic category, Democrats seem to do better among high-turnout voters than demographically identical low-turnout voters. For instance, 96 percent of college-educated registered Democrats who voted in special elections backed Mr. Biden in Times/Siena polling, compared with 83 percent of those who did not vote in specials in the same districts.

This kind of deep advantage is perhaps most easily explained by something like what used to be called “the Resistance” — liberal voters becoming extraordinarily motivated to defeat Republicans since the election of Mr. Trump and again in the wake of Roe’s overturning.

This energy among highly engaged Democrats has powered the party’s victory in special elections, and in 2022 it helped the party hold its own in the midterms.

But the findings suggest there’s not much reason to expect Democrats’ special election strength to persist in the general election, when voters of all kinds — not just the most highly engaged — will show up to the polls.

These differences between special election voters and presidential election voters also suggest there’s not necessarily a contradiction between Mr. Biden’s weakness in the polls against Mr. Trump and Democratic strength in special elections. Voters in special elections tend to be a far more Biden-friendly group than the wider universe of registered voters, which is represented in polls. In these elections, Democrats are almost entirely insulated from Mr. Biden’s weaknesses among young, nonwhite and less engaged voters.

But the special election results nonetheless suggest a modest if still important turnout advantage for Democrats in 2024. Mr. Trump’s weakness among high-turnout voters, like those who participate in specials, and Mr. Biden’s weakness among low-turnout voters may suggest that Mr. Biden is somewhat better positioned than the early polls of registered voters suggest.

Indeed, the last New York Times/Siena College survey found Mr. Biden ahead by two points against Mr. Trump among likely voters, even as he trailed by two points among all registered voters.