Incumbent Losses in 2026 Primaries Exceed Historical Averages, Signaling Potential Shifts in November Midterms

As of September 7, 2026, 2.6% of sitting legislators seeking re-election in 43 states have lost their primaries, surpassing the 2.1% historical average since 2010. This increase is concentrated among Republican incumbents, with 3.3% defeated compared to a 2.6% historical average. Democrats are also fielding candidates in more seats, reducing the number of uncontested legislative districts.