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.