Nearly 30 percent of Los Angeles County’s registered voters cast ballots in Tuesday’s primary election, according to early results. But more than half a million ballots in the county haven't yet been verified and tallied up, and those could still push up turnout numbers and impact close races.

In Los Angeles, Registrar-Recorder/County Clerk Dean Logan estimates there are an outstanding 240,063 provisional ballots, 125,280 vote by mail ballots received at the polls and 204,946 mail ballots received on Election Day.

Turnout should surpass 30 percent in the county once those are included in vote totals. More vote by mail ballots are likely to arrive at the registrar's Norwalk headquarters in coming days, as voters could postmark them as late as Election Day.

About 245,000 ballots remain to be counted in Orange County, according to registrar Neal Kelley. "They very well could have an impact on the races," Kelley told KPCC's AirTalk today.

More than 1.4 million ballots have been processed and counted in Los Angeles County, making up 29.9 percent of eligible registered voters, the registrar's office reported early Wednesday.

"Sadly, a turnout of almost thirty percent is nothing to sneeze at for L.A. County," said Jessica Levinson, a professor at Loyola Law School. "If you look at what was on the ballot, and the fact that the presidential nominees are already decided, that's not particularly surprising."

Levinson said that a competitive presidential primary or a controversial ballot measure could have juiced turnout. But neither factor was present, with the AP declaring that Hillary Clinton had secured the nomination the day before California's primary.

There were 4,909,904 registered voters in the Los Angeles County, according to the secretary of state's office.

Hopes for a strong turnout were high, and in a tweet sent shortly after the polls closed Tuesday, Logan surmised turnout was roughly 40 percent.

Had that number held, it would have marked a big jump over turnout in the last two primaries in California. In 2014, a dismal 17 percent of the county's registered voters cast ballots. And in the 2012 presidential primary, just 21.8 percent of registered voters in L.A. County cast ballots.

Still, Tuesday's returns reverse a downward trend for L.A. County turnout in statewide primaries. Turnout has regularly been below 50 percent since the 1980s, and below 40 percent since 1996. The one bright spot was 2008, when 55 percent of L.A. County voters cast ballots. Hillary Clinton also won in California that year.

Turnout in L.A. County almost always improves between the primary and the general election. Only once in the past 75 years has turnout fallen from the midterm to the general in the county. That was in 1978, which was not a presidential election year.

Statewide as of this morning, turnout came in at about 33.3 percent, according to pre-certified results.

Los Angeles County voter turnout in statewide primary elections since 1996

PRIMARY ELECTION REGISTERED VOTERS BALLOTS CAST TURNOUT VOTE BY MAIL BALLOTS VOTE BY MAIL AS PERCENT OF BALLOTS CAST 2016 4,809,383 1,438,909 29.9% 387,237 26.9% 2014 4,823,407 824,070 17.1% 400,694 48.6% 2012 4,450,035 973,274 21.9% 431,811 44.4% 2010 4,355,447 1,021,448 23.5% 369,499 36.2% 2008 3,951,957 2,183,998 55.3% 482,921 22.1% 2006 3,826,979 1,050,076 27.4% 314,824 30.0% 2004 3,670,157 1,379,747 37.6% 330,353 23.9% 2002 4,142,514 1,070,651 25.8% 218,976 20.5% 2000 3,808,488 1,836,153 48.2% 316,882 17.3% 1998 3,772,593 1,450,126 38.4% 285,532 19.7% 1996 3,620,677 1,346,358 37.2% 257,359 19.1%

Voters in the county cast 256,455 votes in the GOP presidential primary and 1,035,876 ballots in the Democratic contest.

Only about 155,000 independent voters requested cross over ballots to vote in any of the presidential primaries that allowed crossover votes. About 25 percent of registered voters in LA County are registered as no-party-preference voters, and Tuesday they cast about 15 percent of the ballots in the county.

12,778 Angelenos cast ballots in the presidential primary for the American Independent Party. That's fewer than in the 2012 primary, and follows a Los Angeles Times story on how some voters may have mistakenly registered for the party, thinking they were independents.

Turnout in other Southern California counties beat LA County's mark, according to preliminary Secretary of State data. 37.5 percent of Ventura County voters cast ballots yesterday. The figures for Orange and San Bernardino Counties were 34.2 and 30.9 percent, respectively.

Orange County Registrar of Voters Neal Kelley told KPCC's AirTalk he was in the field yesterday and was "encouraged" by the turnout. He noted that it beat turnout in 2012, but fell below turnout for the 2008 primary.

In Riverside County, only 27.5 percent of voters showed up this year.

Sacramento County boasted the highest turnout of any California county with more than 100,000 voters. 56.5 percent of voters cast ballots there. Other Northern California counties boasted turnout north of forty percent, according to the preliminary data, including San Francisco, Santa Cruz and Contra Costa.

"Northern California always puts us to shame in terms of their voter turnout," Jessica Levinson said.

Keep in mind, turnout figures are preliminary and will change. Counties have about 28 days to canvass the ballots and certify the results for the Secretary of State's office. And ballots are still being counted — voters could send in vote-by-mail ballots as late as yesterday.

"We are probably are, you know, seven to 10 days out from getting closer to a more definitive results," Registrar-Recorder Dean Logan told KPCC's AirTalk.

Kelley added that he hoped to finalize results in the next two-and-a-half weeks.

This story has been updated.