I have been wondering about state legislative special elections. They are more numerous than House elections, and therefore are likely a better predictor of results.
Relative to the district's performance in 2020 or 2018 in that same race, excluding races where someone died and a widow(er) is running to replace the deceased member, as well as uncontested races in either November 2020 and the special, which party is leading special elections at the state legislative level? Note I am also excluding states where the normal legislative elections aren't held in presidential years. I am also making it so races with runoffs have only the first round counted and not the runoff election.
(For example, New Mexico's 1st and Louisiana's 2nd are the only two federal/House examples. The Democrats overperformed in both races, by 8 and 13 points respectively.)