A special election was held in Maryland's 7th congressional district on November 29, 1798, to fill a vacancy left by the death of Representative-election Joshua Seney (DR) before the start of the 6th Congress.
Election results
Nicholson took his seat with the rest of the 6th Congress at the start of the 1st session.
References
Maryland's 7th congressional district special election, 1798 Wikipedia(Text) CC BY-SA