Tennant announced her intentions last week, and filed her paperwork Wednesday.
The Democrat joins a growing field of candidates to fill the remainder of former Gov. Joe Manchin’s term. Manchin left office in November after being elected to serve the late Robert C. Byrd’s unexpired U.S. Senate term.
The Legislature recently approved a measure that sets a May 14 primary and an Oct. 4 general.
Other Democrats officially in the race are Senate President Earl Ray Tomblin, House Speaker Rick Thompson and Kanawha County resident Arne Moltis.
Republican Randolph County Sen. Clark Barnes has also filed.
Democratic State Treasurer John Perdue says he’ll announced Friday.