SACRAMENTO (AP) — Preliminary figures show that fewer voters likely turned out for Tuesday’s no-drama primary than for any regular statewide election in California history.

At least 770,000 ballots have not yet been counted from California’s primary election, according to a partial tally posted Thursday by the secretary of state’s office that includes 24 of California’s 58 counties.

The ballots counted so far put turnout about 18.4 percent, although that will certainly grow as elections officials count hundreds of thousands of outstanding ballots, including 166,000 in Los Angeles County.

Two voting experts, Paul Mitchell of Political Data Inc. and Eric McGee of the Public Policy Institute of California, predict turnout will be 22 to 24 percent.

Turnout has been sliding over the last two decades. The previous low for a non-presidential primary was 33.1 percent in June 2010. Turnout hit 28.2 percent in June 2008, an anomaly when the state split the presidential and primary elections.

Tuesday’s contest had few scintillating races to pull in less-regular voters, McGhee said Thursday.

“There’s no presidential contest, no U.S. Senate contest, the gubernatorial race is a snoozer and there are no citizens’ initiatives on the primary ballot anymore,” he said.

Many of the uncounted votes are from permanent absentee voters who receive their ballots in the mail but do not return them by mail. More and more of those voters appear to be getting their ballots early, then sitting on them and turning them in at a polling place on Election Day, Mitchell said.

“Those voters clog up the works,” said Mitchell, who is vice president of Political Data Inc., a consulting firm that tracks voter data.

Others are provisional ballots cast by voters whose names are not found on the rolls at the polling place. Clerks must verify their registration and ensure they have not voted elsewhere before they can count the ballots.

Experts are also closely watching whether who turns out to vote changes with the adoption of the top-two primary, in which the top two vote-getters advance to the general election regardless of party affiliation. Tuesday’s contest was the first statewide election using top-two.

Turnout in California’s primary elections has always skewed generally older, whiter and more conservative than the general electorate, and that appears to have been true on Tuesday. But McGhee said that is more about who the voters are than their political affiliation.

“Republicans are more reliable voters in general,” McGhee said. “They tend to be wealthier, a little better educated, and older. These are all things that tend to make somebody a more regular participant in politics. They are more likely to be homeowners, more established in their communities.”

Registrars have until Friday to report how many ballots are left to be tallied in their counties.