The city would provide public financing for mayoral candidates under a proposal introduced at City Hall Tuesday by Supervisor Ross Mirkarimi.

"Voter-owned elections ensure that politicians are accountable to the public, rather than their campaign contributors,'' Mirkarimi said.

Under the proposal, a candidate could qualify for the public money if he or she raises a combined $25,000 or more from at least 250 San Franciscans. Each contribution must be at least $100. Candidates who accept the money would have to agree to a spending cap.

The fund would be limited to the equivalent of $2 per resident per year. That would amount to a pot of approximately $6 million for mayoral elections, which are held every four years.

San Francisco already provides public financing for Board of Supervisors races.