Record sums have poured through US midterm election contracts this cycle, and the pricing points in one direction: Democratic control of Congress. As of Monday, roughly $1.9 billion in election-related contracts had traded across Kalshi and Polymarket — the highest volume ever recorded for a midterm election cycle — with markets on both platforms pricing a Democratic sweep at approximately 75%.

That headline figure flows directly from how these markets work: prediction-market contracts pay a fixed amount — conventionally $1 per contract or share — if the referenced event occurs, so a market priced at roughly 75% corresponds to contracts changing hands near 75 cents. Because prices move continuously with buying and selling, the number functions as a running, dollar-weighted snapshot of traders' aggregated expectations rather than a single static forecast.

Kalshi operates as a US event-contract exchange regulated by the Commodity Futures Trading Commission (CFTC), allowing traders to buy and sell contracts on the outcomes of real-world events, including elections. Polymarket is a crypto-based prediction market in which participants trade shares tied to event results, with positions settling in stablecoins. Both platforms have emerged as prominent, frequently cited gauges of electoral probability in recent US election cycles, often referenced alongside traditional polling.

Midterm elections, held at the midpoint of a US president's four-year term, feature races for all 435 seats in the House of Representatives and roughly one-third of the Senate, along with numerous state-level contests. In market terminology, a "sweep" refers to a single party capturing control of both chambers of Congress. Chamber control carries procedural significance in Washington, as the majority party in each chamber shapes the legislative agenda and holds committee chairmanships — the outcomes these contracts are written against. Once votes are counted, the contracts will resolve according to the actual results, providing a concrete comparison point between the market's current implied odds and what ultimately happens.

The record $1.9 billion in traded volume underscores the growing scale of political event contracts, which have evolved from niche instruments into widely followed indicators in US election coverage, with the 2026 cycle marking the highest capital turnover yet recorded for a midterm.

This content was first published on COINOTAG: Kalshi and Polymarket Price Democratic Midterm Sweep at 75%