Incumbent Robert Reives II, a Sanford defense lawyer, defeated Barry E. Burns of Chatham County in the Democratic primary with all precincts reporting.
Reives, 43, was appointed to the seat by local Democratic Party leaders, replacing Deb McManus, who resigned after being arrested on felony tax charges.
Burns, 71, a retired teacher and principal, has said he opposes fracking and wants more funding for public schools.
The winner faces Republican Andy Wilkie of Goldston.
The district covers Chatham County and parts of Lee County.