A special election was held in New Hampshire's at-large congressional district on August 25, 1800 to fill a vacancy left by William Gordon (F) resigning to accept an appointment as New Hampshire Attorney General on June 12, 1800.
Election results
New Hampshire electoral law required a majority for election, which was not met on the first ballot, requiring a run-off election on October 27, 1800
Tenney took his seat on December 8, 1800.
References
New Hampshire's at-large congressional district special election, 1800 Wikipedia(Text) CC BY-SA