How many Democratic House Incumbents will not win their Primary?

30-day trend

Analysis

This probability estimates the likelihood that more than 15 Democratic House incumbents will lose their primary elections in 2026. At 24%, the market suggests this is a relatively unlikely outcome, though not negligible. Primary defeat rates for incumbents are historically low—typically under 5% nationally—so exceeding 15 losses would represent a significant departure from the norm. The current pricing reflects several competing dynamics: potential vulnerability from redistricting effects, primary challenges from progressive candidates in certain districts, and retirements that reduce the total pool of incumbents running. The market appears to weight historical incumbent resilience heavily against speculation about heightened primary activity. The outcome will become clearer as primary election dates approach in summer 2026 and filing deadlines pass, with the cumulative results fully resolved by November 2026.

• ›Historical primary defeat rates for House incumbents average 1-3%, making >15 losses a statistical outlier that would require unprecedented primary activity
• ›The total number of Democratic House incumbents running in 2026 remains uncertain; if fewer than 250-280 run, the >15 threshold becomes proportionally harder to reach
• ›Primary challenge intensity varies significantly by region and district competitiveness, with progressive primary challenges concentrated in specific districts rather than broadly distributed
• ›Retirement decisions by incumbents directly affect the denominator and resolved count—ongoing retirements through summer 2026 will clarify the realistic threshold
• ›Competitive primary outcomes depend on candidate quality, fundraising, and local political dynamics in specific districts, which remain fluid rather than predetermined

What moved the line

• May 713-15↓35pp38→3¢ · Polymarket
• May 6<3↓20pp49→29¢ · Polymarket
• May 34-6↓6pp42→36¢ · Polymarket
• May 64-6↑4pp36→40¢ · Polymarket
• May 2<3↑3pp46→49¢ · Polymarket

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These markets stopped trading. Last odds and any captured outcome are shown above — full settlement detail lives at the venue.

How we compute these odds