Help us improve in just 2 minutes—share your thoughts in our reader survey.
U.S. Congress special elections historical data, 1987-2024
This page is updated annually in January.
Between 1987 and 2024, there were at least 33 special elections in the U.S. Senate and 172 in the U.S. House. Ballotpedia compiled, where available, data for these special elections, including the party of the winner, the margin of victory, the number of votes cast, the reason for the special election, and the partisan control of the chamber and White House at the time of the election. The same data was collected for comparative purposes for the preceding and subsequent elections in that district or state.
- In 39 percent of the U.S. Senate special elections during this time period, the seat flipped. Of those flipped seats, 21 percent remained flipped in the subsequent regular cycle election.
- In 16 percent of the U.S. House special elections during this time period, the seat flipped. Of those flipped seats, 75 percent remained flipped in the subsequent regular cycle election.
What else does the data measure?
- Margin of Victory (MOV): How many more percentage points did the winner receive than the second-place finisher?
- MOV Compared to Special Election: How well did the winner of the preceding and subsequent elections perform compared to the candidate from their party in the special election?
- Votes Cast Compared to Special Election: How many more or fewer votes were cast in the preceding and subsequent elections compared to the special election?
How was the data compiled?
Data was compiled from the Federal Election Commission (FEC), state secretary of state websites, and research published by Bloomberg journalist Greg Giroux.
Highlighted rows indicate where a seat flipped during the special election, with red representing a Republican winner and blue a Democratic winner.
The data below is updated annually in January, so it might include special elections that have happened after 2024.
House
Senate
See also
- United States Congress
- United States Senate
- United States House of Representatives
- Filling vacancies in the U.S. Senate
Footnotes
