Sonoma County workers Wednesday set about the laborious task of counting and verifying tens of thousands of mail-in ballots.

Bins of uncounted ballots in the Registrar of Voters' warehouse vividly illustrated the numbers of envelopes yet to be opened and examined by a staff of up to 24 election workers committed to the task.

It likely will take the full 31 days permitted by law to count them, said Janice Atkinson, county elections chief.

That will delay the naming of victors in at least three local elections, and none of the results for any race or ballot measure will be official until that final certification.

In recent general elections, roughly 35,000 mail-in ballots arrive in the mail or hand-delivered to one of the county's 194 polling places on Election Day, making them the last to be counted.

It appeared Wednesday that those numbers would hold true again, said Atkinson, a 40-year veteran of the registrar's office.

"Does it seem to be about usual? Yes, so far," she said.

At the Santa Rosa Veterans Building — Precinct 3112 — 618 mail-in ballots were turned in Tuesday, a record for a single polling station, Atkinson said.

"That's an incredible number," she said.

In total, 184,671 absentee ballots were mailed out to Sonoma County voters — or 71 percent of the county's registered voters — and about 122,000 of those were returned in time to be counted Tuesday.

But the number remaining means that some close races may hang in the balance for weeks:

; The 10th Assembly District race, where San Rafael Councilman Marc Levine claimed victory Wednesday with a 468-vote lead, but Assemblyman Michael Allen refused to concede.

; The Sebastopol City Council race, where incumbent Councilwoman Kathleen Shaffer trailed challenger John Eder by nine votes in a battle for the final contested seat.

; The Santa Rosa school board race, where newcomer candidates Jenni Klose and Brian Noble were separated by 1,055 votes, with Klose leading.

"Those are the highlights," said Gloria Colter, assistant county registrar of voters.

A large number of provisional ballots, filed by voters who said they hadn't received mail ballots or whose status as registered voters couldn't be verified at a polling place, also must be verified and counted.

Many voters requesting provisional ballots had moved residences without re-registering and, said Atkinson, "our lobby was full of them, and I know the polls were full of them" on Tuesday.

Signatures on every ballot are verified by "eyeball," Colter said, a demanding task in its own right. Then, a sampling of ballots from 1 percent of all precincts — or five out of the county's 433 precincts — is manually checked against the computerized tally of votes.

That ensures vote tabulators are functioning correctly, Colter said.

"We always like it not to take that long," she said. "We put our best effort into getting this done."

But the wait has grown longer since 2002, when state law changed to allow all voters to register as permanent absentee voters, pushing up the number of mail-in ballots in circulation, and that can frustrate candidates or people invested in the outcome of a ballot measure.

Still, say experts, the price of lowering barriers to voting is worth the reward.

"We've tried to make it easier, which makes it more likely that people will vote and that's good," said Ed Costantini, a UC Davis professor emeritus of political science. "Anything that enhance the opportunity of people to vote, well, that's a plus to democracy."

The boost in voter activity that mail-in ballots can spur also makes the inconvenience worthwhile, said Dan Schnur, director of the Jesse Unruh Institute of Politics at the University of Southern California.

"If you can increase voter participation and also guard against potential fraud, then waiting an extra couple of days for election results seems like a fairly good trade off," Schnur said.

(You can reach Staff Writer Jeremy Hay at 521-5212 or jeremy.hay@pressdemocrat.com.)