Aftyn Behn won the open Tennessee House seat in District 51 with 75% of the tally over Republican David C. Hooven and one independent.
All were running for the first time for a seat has been held by Democrats since at least 1970.
Behn, the Democrat, has organized lobbying days and protests at the statehouse and was removed from the Tennessee House floor during a demonstration in 2019.
She was endorsed by Moms Demand Action, the Sierra Club, Planned Parenthood and Knoxville Rep. Gloria Johnson, D-Knoxville, who was the lone person among The Tennessee Three who was not expelled.