Kevin Faulconer led a field of 11 candidates with 45 per cent of the vote, according to a large batch of results released minutes after polls closed. His strong showing gives Republicans a chance to recapture an office they held for much of the last four decades and an opportunity for a rare win leading a major American city.
Two Democrats were locked in a close contest to face Faulconer in a likely runoff. Nathan Fletcher, an executive at wireless technology titan Qualcomm Inc. and former state assemblyman, had 25.1 per cent. David Alvarez, a first-term city councilman, had 22.9 per cent.
If no one wins a majority, the top two finishers advance to a runoff.
"We feel really good," Faulconer spokesman Tony Manolatos said. "We absolutely have thought this was going to be a two-step process and we still do. There's going to be a runoff. Everyone's just watching to see who's going to be No. 2."
Filner, the city's first Democratic leader in 20 years, resigned less than nine months into a four-year term after nearly 20 women — including a retired Navy rear admiral and a San Diego State University dean — publicly identified themselves as targets of his unwanted advances, including kissing, groping and requests for dates. He pleaded guilty last month to one felony count of false imprisonment and two misdemeanour counts of battery for his behaviour toward women during his brief time in office.
Filner, a former 10-term congressman, was barely mentioned in campaign mailers or televised debates. But the major candidates have adopted his successful campaign mantra of pouring more money into neglected neighbourhoods, promising to repair crumbling streets and sidewalks and faster fire and ambulance response times.
"Nobody is talking about (Filner) but they're all using his narrative of neighbourhoods first," said Steve Erie, a political science professor at the University of California, San Diego. "They're all talking the talk, but the question is whether they will walk the walk."
Making the Filner debacle a campaign issue carries risk for Republicans because members of the disgraced former mayor's own party were first to expose his behaviour, and national and local party leaders, including Alvarez, quickly demanded that he resign, Erie said. Faulconer also has little to gain by highlighting his Republican credentials in an increasingly Democratic city, he said.
Democrats hold a 13-point advantage over Republicans in voter registration in San Diego. Barack Obama trounced Mitt Romney by 25 points among city voters in last year's presidential election.
Faulconer, 46, announced his bid after about 30 Republican leaders and their allies invited him and other potential contenders to the La Jolla living room of a prominent developer, and the group decided to coalesce around him. During his seven years on the City Council, the mild-mannered former public relations executive was a close ally of Mayor Jerry Sanders, Filner's moderate Republican predecessor. He made one of his biggest splashes by supporting a ban on alcohol consumption on city beaches after a Labor Day melee in 2007 in his oceanfront district.
Fletcher, 36, has eluded easy definition, becoming a Democrat in May, barely a year after bolting the Republican Party to become an independent. He was endorsed by Gov. Jerry Brown, Attorney General Kamala Harris and several law enforcement labour unions.
Alvarez, 33, was backed by the San Diego County Democratic Party Central Committee and the San Diego and Imperial Counties Labor Council, the largest coalition of organized labour.
Associated Press writer Michael R. Blood in Los Angeles contributed to this report.