Market comparison

Which party will win the U.S. Senate?

2 venues · 2 outcome rows · 2 comparable lines · event identity linked · 0 verified parity · active

Kalshi

Open venue ↗

2 outcomes · $17.0M reported volume

Observed 44s ago

Recorded venue end date: Feb 1, 2027

Polymarket

Open venue ↗

9 outcomes · $7.9M reported volume

Observed 44s ago

Recorded venue end date: Nov 4, 2026

Check settlement rules before comparing contracts. Matched outcomes may settle differently. These venues also report end dates more than 48 hours apart; event identity does not mean the contracts close or settle together. These are stored prices; record update times do not certify live quotes. Differences exclude fees and available size.

Known rule differences between venues

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.

A shared identity alone does not make a price difference executable.

Available outcome prices by venue for Which party will win the U.S. Senate?
Outcome	Kalshi	Polymarket	Difference
Democratic Partial parity Payoffs match in ordinary outcomes; see the rule differences above.	68.0% Bid 68.0% · Ask 69.0% Democratic Party Open Kalshi ↗	68.5% Bid 68.0% · Ask 69.0% Democratic Party Open Polymarket ↗	0.5 pp
Republican Partial parity Payoffs match in ordinary outcomes; see the rule differences above.	32.0% Bid 31.0% · Ask 32.0% Republican Party Open Kalshi ↗	31.5% Bid 31.0% · Ask 32.0% Republican Party Open Polymarket ↗	0.5 pp