Midterm control of Congress may remain unclear for a week or more

The outcome of Tuesday's election may not be known for several days, leaving voters and officials without a clear picture of which party controls Congress. The Associated Press is tasked with calling all 435 House districts and the 35 contested Senate seats, but the process often extends well past Election Day.

Control of the House requires 218 seats. Republicans currently hold 219 seats, though two vacancies exist. In the Senate, Democrats need 51 seats while Republicans need 50, as Vice President JD Vance can cast a tiebreaking vote. Republicans currently hold a 53-47 majority.

Historical data suggests a delay is standard. In the 2022 midterm elections, the AP called Senate control four days after the vote and House control eight days later. In 2024, the Senate result was announced the day after the election, but the House call came eight days after that.

Counting timelines vary by state due to voting methods. California, the most populous state, often sees thousands of mail ballots submitted on Election Day. In 2022, half of California's votes were counted after the election. States with key Senate races, such as Alaska and Maine, use ranked choice voting, which can further complicate the count.

Under ranked choice voting, a candidate wins if they secure more than 50% of first-round votes. If no candidate reaches that threshold, the candidate with the fewest first-choice votes is eliminated. Their votes are then redistributed to voters' second choices. This iterative process can stretch the counting period considerably.

The AP does not project winners. It declares a victory only when it determines there is no scenario in which the trailing candidate can close the gap. Until that mathematical certainty is reached, the party controlling each chamber remains uncertain.