Incumbent Garden Grove Mayor Bruce Broadwater is leading in votes by just 1.7 percent, according to the latest tally of votes.
According to the OC Registrar of Voters, only 75 percent of ballots have been counted, with 25 percent that are still outstanding.
The current tally shows Broadwater leading with 43.2 percent compared to 41.5 percent of the vote for his opponent, Garden Grove School Board Trustee Bao Nguyen.
At 76, Broadwater is fighting allegations of nepotism and favoritism in the hiring of his 37-year-old son Jeremy as a firefighter despite a criminal record and poor performance reviews from his superiors.
Broadwater has denied any notion that he intervened in his son's hiring and has said the fire union, which has been outspoken about his son's hiring, is politically motivated in its complaints.
He has defended his tenure by pointing to the city's fiscal soundness and the number of big development projects on the horizon that he argues will attract tourists, jobs and much-needed revenue to the city.
A Democrat and member of the OC Fair Board, Nguyen launched his campaign amid sharp criticism of Broadwater, running on a platform of transparency and access to city hall.
He also called for a development strategy aimed at keeping young professionals and recent college graduates in the city.
At The Globe restaurant on Main Street, where Nguyen hosted his election night party, many of his young supporters signaled the battle was not over in Garden Grove.
"This is a city that puts very little value on its young residents. We have a generational problem," said John Quiggle, who grew up in Garden Grove and works at two restaurants on the city's Historic Main Street.
In the race for city council, former planning commissioner Phat Bui finished first with 23.5 percent, followed by incumbent councilman Kris Beard, who finished with 23.2 percent of the vote.