Voter turnout for the Nov. 8 election so far is about 15,000 -- with tens of thousands still expected to roll in -- if this year’s turnout matches past years involving mayoral races.

Most of the returned ballots were mailed in, with 1,100 others coming from voters at an early polling station on the ground floor of City Hall. Early voting in San Francisco began on Oct. 11.

Department of Elections director John Arntz said 203,000 ballots were mailed to voters and that the average turnout for cycles with mayoral hopefuls is about 50 percent.

“It’s about what we expect,” Arntz said of the turnout so far.

Arntz said he’s anticipating an acceleration of returned ballots as the days grow closer to Nov. 8, with the biggest daily pile of returns – maybe 25,000 to 35,000 – rolling in on Election Day. Tabulation of ballots begins Monday, but machines don’t actually start counting votes to determine winners until the polls close and the election season’s clock officially runs out.

“We don’t press that button until election night,” Artnz said.

dschreiber@sfexaminer.com