The first returns in Tuesday’s special election for county supervisor show Chula Vista Mayor John McCann and Imperial Beach Mayor Paloma Aguirre in the lead to advance to a runoff later this year.

It’s election day for voters in the South Bay, where seven people — including four elected officials — are vying to fill the District 1 seat on the San Diego County Board of Supervisors, which was vacated by Nora Vargas.

A total of 13 vote centers will open in San Diego's First Supervisorial District Tuesday as the final day of voting to replace former San Diego County Supervisor Nora Vargas begins.