SAN DIEGO (CNS) - Two of the former supporters of Bob Filner who later became among the first to call on him to resign over his behavior as mayor announced their endorsements for his replacement Thursday.

Councilman David Alvarez won support from ex-Councilwoman Donna Frye.

"David is dedicated to ensuring that all members of our San Diego communities have a voice in decisions that impact their quality of life," Frye said. "He understands that he is a public servant and knows that the needs of the public come first."

Frye worked as Filner's director of open government until she resigned in April. She later joined with attorneys Cory Briggs and Marco Gonzalez in accusing Filner of sexual harassment and demanding he step down. Filner left office Aug. 30.

While endorsing Alvarez, she called for humility and courtesy in the mayor's office.

"With David, what you see is what you get," Frye said. "He's grounded and comes from a family who instilled in him core beliefs and values that are based upon respect for all members of our San Diego communities."

Gonzalez threw his support behind ex-Assemblyman Nathan Fletcher.

"When it comes to the environmental issues most important to me and those I represent, Nathan is the only candidate with the vision and leadership capabilities to effect real change," Gonzalez said. "He will bring a much needed energy and focus to the mayor's office, and I look forward to standing with him as we tackle the significant challenges ahead."

Before kickstarting Filner's downfall, Gonzalez was best known for his lawsuits that sought to eliminate fireworks displays over sensitive marine habitats off San Diego's coastline.

Meanwhile, the first debate of the campaign was set for Friday afternoon. It's scheduled to take place as part of the 2013 California Asian Business Summit at the Westin Gaslamp Quarter in downtown San Diego.

Former City Attorney Mike Aguirre, Alvarez and Councilman Kevin Faulconer are scheduled to participate. Fletcher, who is speaking to summit attendees separately, will not take part.

Friday is also the deadline for prospective candidates to file nomination papers with at least 200 valid signatures to the City Clerk's Office.

The special election is set for Nov. 19. If no one wins a majority of the vote, a runoff between the top two vote-getters would be scheduled for early next year.