SAN DIEGO — Interstate 8 has long been a political divide in San Diego and maybe never more than in the campaign to replace Mayor Bob Filner, who resigned amid a torrent of sexual harassment allegations.

Republican Kevin Faulconer, a city councilman, easily topped a field of 11 candidates in a first round of voting by dominating in newer, wealthier neighborhoods north of the freeway. Democrat David Alvarez, also a councilman, finished second by cleaning up south of the freeway in more densely populated, predominantly Latino areas.