Polymarket (via UMA optimistic oracle)
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Rules
This market will resolve according to the party that wins control of the United States Senate and the party that wins control of the United States House of Representatives in the 2026 United States midterm 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 holds the Vice Presidency. 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.
A party wins control of the United States House of Representatives if it wins a majority of the chamber’s voting seats. If no party wins a majority of voting seats, the chamber will be deemed controlled by the party with which the first elected Speaker of the House of the Congress that convenes after the 2026 midterm election is affiliated.
The following rules govern the counting of seats for determining which party wins control of the chambers.
For determining Senate control, all regular and special Senate elections that determine representation in the upcoming 120th Congress and are scheduled to take place in November 2026 as of October 31, 2026 are included. Vacant Senate seats for which no election or special election to fill the seat is scheduled to take place in November 2026 as of October 31, 2026 will be treated as held by the party affiliation of the most recent member to hold that seat. For determining House control, all House elections in the 2026 United States midterm election that elect voting members and determine representation in the upcoming 120th Congress are included. Where a Senate or House seat is decided by a runoff, the runoff result will determine attribution of that seat, even if it takes place after November 2026.