Midterm Seat Loss Calculator
An interactive calculator that predicts U.S. House seat change for the president's party based on net approval rating at the time of the midterm. The model is a linear regression fit on every U.S. midterm election since 1946.
Key finding
Presidential approval is a weaker predictor of midterm seat change than commentary typically implies. The R² is modest and the 90% prediction interval is wide — often ±30 seats or more. The president's party usually loses seats regardless of approval, but the exact magnitude has high uncertainty.
How it works
- Adjust the president's net approval rating (approve minus disapprove).
- The regression returns a predicted seat change along with a 90% prediction interval.
- A scatter plot shows every historical midterm as a data point so you can see how far the prediction really travels.
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By G. Elliott Morris, author of Strength In Numbers.