20% — Will the Democratic Party hold less than 45 seats in the 120th Congress
Leader: Above 52 at 20% · Kalshi 20% · 19 contracts · $17K volume · medium confidence
Updated 2026-06-08 08:45:00 UTC

Tracks the leading outcome in a winner-take-all prediction market set with 19 outcomes.

Why this matters:
This probability reflects the chance that Democrats will control fewer than 45 Senate seats following the 2026 midterm elections. The current 34% estimate reflects expectations that Democrats will likely retain Senate control or remain competitive, though significant uncertainty remains. The probability is primarily driven by historical midterm patterns favoring the opposition party and the electoral map, which features both Democratic-leaning seats in swing states and Republican-held seats in unfavorable terrain. The resolution depends entirely on the November 2026 midterm election results, which will determine the final Senate composition of the 120th Congress. Notably, related markets show substantial disagreement—Polymarket implies a much higher probability of Democratic underperformance than Kalshi, suggesting traders disagree on either baseline Senate dynamics or specific race outcomes.

Key factors:
- Current Senate composition and which seats are up for election in 2026 will mechanically constrain the range of possible outcomes
- Historical midterm patterns show the party holding the presidency typically loses Senate seats, but magnitude varies significantly based on economic conditions and approval ratings
- The 39-point spread between Polymarket and Kalshi contracts suggests material disagreement on Democratic performance, possibly reflecting different assumptions about candidate quality, turnout, or national environment
- Senate race-specific data points like the South Carolina Democratic market priced at 15¢ indicate expected losses in certain red-state Democratic seats
- The Democratic-majority prediction market (84¢ on Kalshi) implies traders expect Democrats to hold the chamber overall, making a sub-45-seat outcome a tail risk scenario

Contracts:
- Will the Democratic Party hold more than 52 seats in the 120th Congress?: Above 52 — 20¢ Kalshi $2K (weight 13%)
- Will the Democratic Party hold 50 seats in the 120th Congress?: 50 — 16¢ Kalshi $17 (weight 0%)
- Will the Democratic Party hold 51 seats in the 120th Congress?: 51 — 15¢ Kalshi $14K (weight 79%)
- Will the Democratic Party hold 49 seats in the 120th Congress?: 49 — 15¢ Kalshi $250 (weight 1%)
- Will the Democratic Party hold 48 seats in the 120th Congress?: 48 — 10¢ Kalshi $0 (weight 0%)
- Will the Democratic party hold exactly 45 Senate seats in the 121st Congress?: 45 — 10¢ Kalshi $0 (weight 0%)
- Will the Democratic Party hold 52 seats in the 120th Congress?: 52 — 9¢ Kalshi $1K (weight 6%)
- Will the Democratic party hold fewer than 45 Senate seats in the 121st Congress?: Below 45 — 9¢ Kalshi $0 (weight 0%)
- ... and 11 more

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## Methodology

SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours.

## SF Signal

- SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration.
- No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only.

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*Last verified: 2026-06-08T08:20:08.176Z*

By SimpleFunctions — https://simplefunctions.dev/

Cite as: "20% per prediction markets (SimpleFunctions, June 2026)"
Canonical: https://simplefunctions.dev/answer/dsenateseats
Full data: https://simplefunctions.dev/api/public/query?q=Will%20the%20Democratic%20Party%20hold%20less%20than%2045%20seats%20in%20the%20120th%20Congress
Provider: SimpleFunctions — https://simplefunctions.dev