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Verification: Historical seat changes and DDHQ’s dated November 3 forecast announcement (84% Democratic House-control probability; 241-seat projection) have been checked. Independent reporting corroborates control of both chambers. These external citations do not fully verify the supplied November 4 race-level dataset, polling averages, or ratings. The regression outputs have not been independently re-estimated, and the attributed Silver Bulletin 240-seat estimate remains uncorroborated. The infographic describes that fixed, preliminary, partially unverified dataset, not certified totals.
The forecasts anticipated Democratic gains. The harder question was how far those gains would reach.
In the supplied November 4 snapshot, the typical House district shifted 14.3 points toward Democrats relative to its 2024 presidential margin. That movement was unusually widespread across districts with very different political histories.
One simple model makes the distinction clear: pre-election inputs imply 243 Democratic seats; the swing observed after the election implies 262. A 19-seat difference. Same model, different information. These are model estimates, not official results.
Using the observed swing, the rule correctly classifies 95.7% of the 392 called House races. That is a retrospective, in-sample fit, not a pre-election forecasting record.
The challenge wasn’t just predicting who would win. It was estimating the size of the shift. The infographic summarizes a preliminary, partially unverified dataset; verified external citations do not constitute a complete audit of its race-level inputs.
Full analysis: https://j-abed.github.io/one-parameter-model-2026-midterms
#DataScience #Forecasting #Statistics
What Everyone Missed About the 2026 Midterms. A 14.3-point median Democratic swing was widespread across House districts relative to their 2024 presidential margins. The same model implies 243 Democratic seats with a pre-election swing estimate and 262 with the observed swing: a 19-seat difference, not official election results. The rule correctly classifies 95.7% of 392 called races using the observed swing, a retrospective, in-sample result rather than a forecast. The challenge was estimating the size of the shift. Unverified supplied November 4, 2026 snapshot. Jason Abed.