Sonoma County has issued nearly 185,000 vote-by-mail ballots for Tuesday's election, a record that represents 71 percent of registered voters.
But it also means any close race, such as the 1st District supervisorial contest between Santa Rosa City Council members Susan Gorin and John Sawyer, may remain unresolved for up to four weeks after the election.
The burgeoning number of absentee voters, along with high voter participation and a lengthy ballot in the presidential election, virtually guarantees officials will need the full 28 days allowed by law to tally the vote, county elections chief Janice Atkinson said Thursday.
"It will take everything we can do to make that" deadline, she said.
One of the major delays will be the painstaking process of verifying an estimated 35,000 vote-by-mail ballots expected to arrive in Tuesday's mail or turned in at polling places Tuesday.
Only vote-by-mail ballots returned by 5 p.m. Monday can be counted on Election Night, along with the traditional ballots cast at the polls on Election Day, Atkinson said.
She is expecting about 186,000 votes to be counted on Election Night, based on an estimated 85 percent overall turnout by county voters.
If her forecast is correct, nearly 16 percent of the total vote -- the 35,000 vote-by-mail ballots delivered Tuesday -- will not be counted for at least three weeks after Election Day, potentially clouding the outcome of races with razor-thin margins.
In the June primary, about 23,250 vote-by-mail ballots came in on Election Day, and it took 22 days to report the county's final results, including Gorin's 186-vote advantage over Sawyer.
With 184,671 absentee ballots issued and 260,448 registered voters, Sonoma County had one of the highest rates -- 71 percent -- of absentee voting in California.