Kalshi and Polymarket: How US Midterm Election Contracts Are Trading
United States.- 15 October 2026 | www.zonadeazar.com Prediction markets in the United States are recording substantial activity linked to the November 2026 midterm elections, when voters will elect the entire House of Representatives and a portion of the Senate.
According to a DeFi Rate snapshot from 14 October 2026, at 7:51 am ET, contracts traded on Kalshi and Polymarket reflected a 62.4% market-implied probability of Democratic Senate control and a 90.3% implied probability of Democratic control of the House of Representatives.
The figures provide a snapshot of expectations expressed through contract prices, highlighting the growing importance of prediction markets within the US trading industry.
Senate Control: Kalshi and Polymarket Prices Differ
The report compares quotations from two leading prediction market platforms.
Contracts concerning control of the Senate showed:
- Kalshi: 61.3% implied probability of Democratic control.
- Polymarket: 63.5%.
- Average across both platforms: 62.4%.
The methodology uses the midpoint between available bid and ask prices.
On Kalshi, the Senate indicator is constructed from two contracts covering different combinations of congressional control.
On Polymarket, the figure comes directly from a contract concerning control of the Senate.
House of Representatives: Prices Close to 90%
Differences between the platforms were smaller for contracts linked to the House of Representatives.
DeFi Rate recorded:
- Kalshi: 90.05% implied probability of a Democratic majority.
- Polymarket: 90.5%.
- Average: 90.3%.
A party needs at least 218 seats to secure a majority in the House.
Both markets incorporate this requirement into their respective settlement rules.
The prices represent participants’ market valuations and should not be confused with election polling or confirmed results.
Republican Control of Both Chambers
The report also examines contracts linked to the possibility of the Republican Party retaining simultaneous control of the Senate and House of Representatives.
The prices were:
- Kalshi: 10.5%.
- Polymarket: 8.5%.
- Average: 9.5%.
These instruments allow participants to trade directly on different combinations of congressional control.
Their prices provide insight into how market participants value potential distributions of political power within Congress.
Analysis of 35 Senate Elections
Beyond national control contracts, DeFi Rate developed a calculation using quotations from 35 individual Senate election markets available on Kalshi.
The methodology combines the implied probabilities for each state with the Senate seats not being contested in 2026.
Under a statistical assumption that the elections are independent, the calculation produces an aggregate value of approximately 64% for Democratic Senate control.
However, DeFi Rate acknowledges that state elections are not completely independent events.
Changes in the national political environment can affect multiple states simultaneously, meaning the calculation should be understood as a methodological exercise rather than a directly traded market price.
Alaska, Michigan and Texas Among Featured Markets
The snapshot also includes contract prices for individual Senate elections.
Selected readings included:
- Alaska: 73.5% for the Democratic candidate.
- Michigan: 67.5%.
- Texas: 63.5%.
- Ohio special election: 59.5%.
- Maine: 56.5%.
All these figures were derived from Kalshi contracts.
Other states recorded different prices. For example, Democratic contracts were trading at 40.5% in Iowa and 36.5% in Kansas.
The figures illustrate variations across state-level prediction markets, although they do not represent direct measurements of voter intention.
Markets With More Concentrated Prices
The platform also recorded contracts with implied probabilities above 95% in several states.
These included:
- Colorado: 98.45% for the Democratic candidate.
- Rhode Island: 98.1%.
- Massachusetts: 98%.
- Delaware: 97.9%.
- Oregon: 97.85%.
- Illinois: 97.75%.
- Virginia: 97.45%.
However, DeFi Rate identified several of these quotations as stale, reflecting the time elapsed since their most recent update.
They therefore did not necessarily represent prices available for execution when the snapshot was recorded.
Understanding Event Contract Prices
On platforms such as Kalshi and Polymarket, participants trade contracts linked to future events.
When a contract pays a fixed amount if a particular outcome occurs, its price can be interpreted as an implied probability.
For example, a contract priced at 60 cents that pays one dollar if the event occurs corresponds to an implied probability of approximately 60%.
However, this interpretation must consider:
- Market liquidity.
- Bid-ask spreads.
- Trading fees.
- Contract settlement conditions.
- The age of available quotations.
Contract prices reflect traded market valuations and do not guarantee future outcomes.
Kalshi and Polymarket Expand Political Market Coverage
Congressional elections represent an important category within the US prediction markets industry.
Available contracts cover national outcomes, control of legislative chambers and individual state elections.
DeFi Rate’s data demonstrate how products from different platforms can be compared through price aggregation methodologies.
However, the underlying contracts are not always identical, as illustrated by Kalshi’s constructed Senate control indicator.
Comparisons therefore require careful consideration of contract specifications to avoid misleading interpretations.
Next Steps and Impact
The 14 October 2026 snapshot provides a detailed reference for prediction market pricing ahead of the US midterm elections.
Its principal readings included 62.4% implied probability of Democratic Senate control, 90.3% for the House of Representatives and 9.5% for Republican control of both chambers.
The publication also includes data from 35 state-level Senate markets and a methodology for comparing contracts across different platforms.
These prices will continue changing as new transactions occur and market participants respond to additional information.
For the iGaming and prediction markets industries, monitoring these contracts provides insight into how political event trading is structured and commercialised in the United States.
Editó: @fonta
