The Prediction Markets

Which party will win the Senate in 2028?

Closes
Nov 8, 2028, in 24 months
Traded
$131K
Venues
Polymarket, Kalshi
Prices updated
44 min ago
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What the markets expect

Democratic 87.3%

Next is Republican at 12.7%. The venues differ most on Republican (Polymarket 11.5%, Kalshi 13%), a 1.5-point gap.

Democratic 87.3%Republican 12.7%

Odds by venue

Fair chance strips out each venue’s built-in margin (its prices add up to more than 100%), then blends the venues by how much has traded there, so the outcomes add up to 100%. Best Yes price is the cheapest ask across venues, and the payout is what a winning $100 stake returns before fees. Open a row for each venue’s contract name, bid and ask, and how closely their rules match.

Prices come from our regular polls of each venue, the oldest 45 min ago. Ages are as of when this page was built.

  • Polymarket
  • Kalshi
Democratic
87.3%
Polymarket 86.5%(88.3% fair)polled, 45 min agoKalshi 87%polled, 44 min agoBest Yes 88¢ on Polymarket, $100 pays $114 (1.14x)
Polymarket
Contract
Democratic Party
Last price
86.5%
Fair, margin removed
88.3%
As of
Polled 45 min ago
Buy Yes
88¢
Sell Yes
85¢
$100 on Yes pays
$114 (1.14x)
Volume
$3K
Trade this on Polymarket
Kalshi
Contract
Democratic party
Last price
87%
As of
Polled 44 min ago
Buy Yes
88¢
Sell Yes
87¢
$100 on Yes pays
$114 (1.14x)
Volume
$87K
Trade this on Kalshi
Partial parity

Payoffs match in ordinary outcomes; see the rule differences below the table.

Indicative only, prices are 45 min old: No arbitrage: the best bid elsewhere is 87¢, at or below the cheapest ask of 88¢.

Republican
12.7%
Polymarket 11.5%polled, 45 min agoKalshi 13%polled, 44 min agoBest Yes 12¢ on Polymarket, $100 pays $833 (8.33x)
Polymarket
Contract
Republican Party
Last price
11.5%
As of
Polled 45 min ago
Buy Yes
12¢
Sell Yes
11¢
$100 on Yes pays
$833 (8.33x)
Volume
$1K
Trade this on Polymarket
Kalshi
Contract
Republican party
Last price
13%
As of
Polled 44 min ago
Buy Yes
13¢
Sell Yes
12¢
$100 on Yes pays
$769 (7.69x)
Volume
$40K
Trade this on Kalshi
Partial parity

Payoffs match in ordinary outcomes; see the rule differences below the table.

Indicative only, prices are 45 min old: No arbitrage: the best bid elsewhere is 12¢, at or below the cheapest ask of 12¢.

No cross-venue arbitrage right now: on every matched outcome, the best bid on one venue is at or below the cheapest ask on the other. Find markets with open spreads

Mostly the same bet: 4 differences

Where they differ

  • Kalshi: media-consensus call, otherwise the party of the Speaker / President pro tempore on Feb 1 of the new Congress. Polymarket: majority of voting seats as elected, independents by caucus.
  • Tied Senate: Polymarket awards the Vice President's party; Kalshi follows the President pro tempore.
  • Members switching party after election day change the Kalshi outcome but not Polymarket's.
  • Trading closes at different times: Nov 8, 2028, 4:59 AM UTC on Polymarket and Feb 1, 2029, 3:00 PM UTC on Kalshi.
Polymarket
Polymarket resolves via:
UMA optimistic oracle
Kalshi
Kalshi resolves via:
Kalshi (CFTC-regulated exchange), source: Library of Congress
Show full rule comparison
  • Kalshi: media-consensus call, otherwise the party of the Speaker / President pro tempore on Feb 1 of the new Congress. Polymarket: majority of voting seats as elected, independents by caucus.
  • Tied Senate: Polymarket awards the Vice President's party; Kalshi follows the President pro tempore.
  • Members switching party after election day change the Kalshi outcome but not Polymarket's.
  • Trading closes Nov 8, 2028, 4:59 AM UTC on Polymarket and Feb 1, 2029, 3:00 PM UTC on Kalshi.

Summarized from each venue’s published rules; the venue’s own rules page is the final word.

How the odds have moved

The top 2 outcomes on both venues, with the consensus between them. Hover for exact values.

  • Democratic
  • Republican

Live prices for Democratic

What it costs to buy Yes, what you would get selling it, and the last trade on each exchange, updating as orders change. Hover a status for timing details.

Order books

Each venue’s resting orders for the selected outcome’s Yes contract, side by side. Top of book streams live; depth refreshes every 15 seconds.

Combined depth · both venues

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Depth · top 8 levels

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Recent trades

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Top of book

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Depth · top 8 levels

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Recent trades

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What your stake buys

Enter a stake to see where it buys the most after fees, using each venue’s live order book.

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Cover all 2 outcomes across venues

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Buys at the asks resting now (taker orders), cheapest after fees first, from order-book snapshots up to 15 seconds old. Fees: Kalshi 0.07 × price × (1 − price) per share, rounded up to the cent; Polymarket 0.04 × price × (1 − price) per share (politics rate). Fee calculator. Estimates only, not advice.

About this market

Live prediction market odds for "Which party will win the Senate in 2028?". Democratic leads at 87.3%. Next is Republican at 12.7%. $131K has traded across 2 outcomes on Kalshi and Polymarket. The market is expected to resolve by Nov 8, 2028.

This market will resolve according to the party that wins control of the United States Senate in the 2028 United States general election. A party wins control of the United States Senate if it wins a majority of the chamber’s voting seats. If no party wins a majority of voting seats, the party that wins control of the chamber is the party that wins half of the voting seats and wins the Vice Presidency in the 2028 United States Presidential Election. If the outcome remains ambiguous after applying the above criteria, the chamber will be deemed controlled by the party with which the first selected President Pro Tempore of the Congress that convenes after the specified election is affiliated. The following rules govern the counting of seats for determining which party wins control of the chamber. All regular and special Senate elections that determine representation in the upcoming 121st Congress and are scheduled to take place in November 2028 as of October 31, 2028 are included. Runoffs for qualifying elections will determine attribution of the relevant seat, even if they take place after November 2028. Vacant seats for which no election or special election to fill the seat is scheduled to take place in November 2028 as of October 31, 2028 will be treated as held by the party affiliation of the most recent member to hold that seat. For seats contested in the specified election, seats are attributed to the party under which the member was elected. If a member-elect changes party affiliation, or vacates their seat, between election day and the formal organization of Congress, the seat is attributed to the party under which the member was elected. For seats not contested in the specified election, seats are attributed to the party that holds the seat as of the date of the election. If a current sitting member of the U.S. Senate who is not up for election changes party affiliation or vacates their seat after the date of the election, the seat is attributed to the party under which the member was affiliated at the time of the election. Senate members elected as independents who formally caucus with, or, for newly elected members, who announce their intent to caucus with, a party are included in that party’s count. If the caucus decisions of members of the Senate elected as independents cannot be determined on the date of the election, this market may remain open until the earlier of (i) an announcement from the relevant members of their intents to caucus, or (ii) January 4th, 11:59 PM ET of the following calendar year. If no such announcement is made by January 4th, 11:59 PM ET of the following calendar year, the member will not count towards the seat count of any party. The resolution sources for this market will be official information from relevant state electoral authorities, the United States Congress, and a consensus of credible reporting.

Questions

What does the consensus price mean?

It is the price of a Yes contract that pays $1 if the outcome happens. A 14¢ price means traders put the chance near 14%. Where two venues list the same outcome, we blend their last prices, weighting the venue with more trading volume more heavily (neither counts for less than a quarter). When only one outcome can win, each venue’s prices add up to a little over 100% (its margin); the fair chance removes that margin so the outcomes add up to exactly 100%.

How is the payout worked out?

A Yes contract pays $1 if it wins, so at the best ask a $100 stake buys 100 ÷ ask contracts. At 18¢ that is about 555 contracts, paying $556 (5.56x) if Yes happens. Venue fees and price slippage on larger orders are not included.

Why do the venues show different prices?

Each venue has its own traders, fees and order book. Contracts can also settle on slightly different terms, which is why each row lists how closely the rules match.

Is a price gap an arbitrage?

Only when you can buy Yes on one venue below what someone pays for Yes on the other, after fees, and both contracts settle the same way. We show the executable bid and ask so you can check.

How fresh are these prices?

Venue prices refresh every few minutes, and the order book and live quotes stream continuously. Each venue’s card shows when we last observed it.

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