Will the Republican Party hold below 190 House seats after the 2026 midterm elections?

Logged 1 Nov 2026, 18:01 UTC · Brier 0.5968

• The Republican Party, as the president's party, enters the midterm with a historically high probability of losing seats (18 out of 20 midterms).
• To resolve YES, Republicans must lose at least 29 seats from their current 218. This is a very large loss, exceeding the historical average midterm loss of 27 seats for the president's party.
• A loss of 29 or more seats constitutes a 'wave' election. While possible, such a large loss is significantly less likely than a more modest loss consistent with the historical average.
• Given the extremely low probability of the required seat swing, the probability of the Republican Party holding below 190 seats is minimal.

What would change it: Widespread and reliable polling data indicating a catastrophic, unprecedented collapse in support for the Republican party just before the election.

-17.8 probability points from the market at generation · high confidence · Polymarket

Base rate: In the 20 U.S. midterm elections from 1946 through 2022, the president’s party lost House seats in 18 elections, a base rate of 90% for the president's party losing seats.

Chosen by Crossbook's published selection rule (auto-v2), not by hand.

Formed blind at 5.0%, without sight of the price; published at 22.8%, the market’s 40.5% moved 50% of the way toward it by fixed rule. None of the cited facts could be shown to be one the market had not already priced. That check is recorded, not enforced.