Despite Belcher's wide margin of victory, Watson said that Belcher's positions on several issues "are totally out of step with the values of the voters of the 49th district and we will work to make sure the people of Bullitt County are kept up to date on her actions in Frankfort so she can be held accountable for her votes".
Belcher's Tuesday victory marks the 37th state legislative seat that Democrats have picked up since Trump was elected.
The two vied for the seat vacated by Johnson's husband, the late Rep. Dan Johnson, who died by suicide in December after an investigative reporting team published a story saying he had molested a teenager at the church where he was a pastor, and linked him to arson cases and alcohol violations, also at the church.
The Kentucky district is the 18th formerly Republican-held district to fall into Democratic hands in a special election since Trump won the election.
Despite the lopsided results, Johnson refused to concede, citing "widespread voter fraud". Bullitt County Clerk Kevin Mooney said the problem was fixed and poll workers were instructed to send affected voters to another precinct.
Belcher, former school teacher and principal, also entered politics after her husband died in a 2008 auto accident. 'It's like we are in a third world country'. If she wins, she would face Belcher again in the general election.
Belcher said it was "hard to say" if sexual assault allegations against Dan Johnson and his death played a part in the election, adding: "I have tried to stay very positive and away from that whole situation".