Santa Ana, Calif. (AP) — The contest Tuesday to fill a vacant Southern California Assembly seat will go to a runoff, after no candidate cleared 50 percent of the vote needed to win outright.

The heavy favorite to claim the Orange County seat will be county supervisor Chris Norby, a Republican who led the five-candidate field with 37 percent of the votes, according to unofficial returns with all precincts reporting. Turnout was light, with only about 17 percent of registered voters casting ballots.

Five candidates ran in the 72nd Assembly District to replace Mike Duvall, a Republican who resigned in September after being caught on videotape bragging about kinky romps with lobbyists. The married father of two claimed his only offense was “inappropriate storytelling.”

Since no candidate cleared the majority threshold, a runoff will be held Jan. 12 with the top vote-getter from each party. Democrat John MacMurray and Green Party candidate Jane Rands also advanced.

Norby will hold a commanding edge in the contest in the Republican-leaning district that includes the cities of Fullerton, Anaheim, Placentia, Orange, Brea, Yorba Linda and La Habra.

The race to replace Duvall was mostly a showdown between Norby and Republican National Committee member Linda Ackerman. The two traded relentless attacks over personal ethics. She got about 20 percent of the votes while the third Republican on the ballot, Richard Faher, received 13 percent.

The outcome will not tilt the balance of power in the 80-seat Assembly, where there are 50 Democrats, 28 Republicans and one independent.