This report has been updated to include data through Sunday, March 3.

Early voting for the Tuesday, March 5 primary is creeping along towards what could be a record low turnout in Santa Clara County and across the state.

Elections offices mailed out vote-by-mail ballots Feb. 5 and opened early in-person voting centers in Santa Clara County last Saturday. As of Sunday, March 3, less than 15% of the more than one million registered voters in the county had cast ballots. As of Feb. 28, the number of returns was barely 11%.

While the daily rate of returned mail ballots was increasing last week, it accelerated only slightly on the weekend. The county Registrar of Voters reported 152,181 mail ballot returned and accepted as of March 3, 14.4% of the total.

Local election officials said this week they expect a surge this weekend. The county’s two highest daily totals of returned mailed ballots were 12,710 on Feb. 29, and 12,134 on March 2.

In the 16th Congressional District, perhaps the most hotly contested primary race, with 551,203 ballots mailed to Democrats, just 16.3% -- 89,456 -- had been returned as of Monday. Democratic turnout for 17th, 18th and 19th congressional district all was less than 16% as of Monday. All of the contested races for Santa Clara County supervisor also were under 20% as of Monday.

Among the county's 13 cities, only Palo Alto report more than 20% Democrat returns
by Monday. Next highest numbers of ballots were the two incorporated town, Los Altos HIlls and Los Gatos, with about 19%.In California’s last presidential primary, in 2020, voter turnout in Santa Clara County was a little over 52% (of registered voters.) In the presidential primary ballot before then, in 2016, the statewide turnout was nearly 55%.

The primary turnout in the county in 2022 was just under 36 percent, and this year’s county tally is likely to be under 30%, based on this week’s trends. In the June 2012 presidential primary in California, when incumbent Barack Obama won re-election, the statewide turnout was just under 39% in the county and about 31% statewide, the lowest ever.

While most votes will be counted by Tuesday evening, final, unofficial vote totals likely won’t be announced until after the March 12 vote-by-mail deadline, election officials said.

Ballots can be dropped off at any of the 102 official drop boxes in Santa Clara County, open 24/7 or one of the 23 voting centers opened last Saturday or the additional 81 voting centers to open this Saturday, March 2 by Tuesday at 8pm.

“Vote Centers offer a traditional voting experience, with the added benefit of giving voters the freedom to cast their ballot at any location in the county,” said Shannon Bushey, Registrar of Voters. “All Vote Centers are fully-equipped to handle any voting need,” including same-day voter registration.

Vote Centers will be open daily from 9am to 5pm or 10am to 6pm, depending on the location. On Election Day, March 5, all vote centers will be open from 7am to 9pm.

For years the designation of Election Day has been a misnomer, as California voters increasingly vote by mail before that official day. This year, it is anticipated that 95% of votes will have been cast by mail, rather than by in-person voting on (or before) “Election Day” by 8pm Tuesday, when polls “close.” Any mail ballots postmarked on Tuesday and received before March 12 will be counted.

The absence of any real contests in either the Democratic or Republican presidential primaries is considered the major explanation for the lack of voter interest, despite a wide range of contested local races, especially in the 16th Congressional District, where 11 candidates are seeking the seat left open by the retiring Anna Eshoo.

The voting choices differ according to political party affiliation. For the U.S. Senate, U.S. House and state legislative races, California holds an “open” primary.  Voters, no matter how they’re registered, can pick anyone of any party.

This means you don’t have to be a registered Republican to vote for a Republican candidate in the U.S. Senate primary — you can do that if you’re registered with no party preference or another party, even if you’re a Democrat.

And if you want to vote for one of the Democrats in the race, you’ll have that option even if you’re a registered Republican.

The top two vote-getters, regardless of party affiliation, advance to the November general election.

But it’s different for the presidential primary.

You can only cast a ballot on the Republican side — at this point, a choice between frontrunner Donald Trump and challenger Nikki Haley — if you are registered in California as a Republican. The state GOP has chosen to stage a “closed” presidential primary, which also means that voters registered with no party preference cannot participate. (The same applies to the Green and Peace and Freedom parties).

The California Democratic Party allows even voters who aren’t registered Democrats to vote in its presidential primary — although there’s a catch. Unaffiliated voters — who are otherwise set to receive ballots that don’t have the presidential race on it — will need to request a ballot that includes the presidential race. (The American Independent and Libertarian parties also allow no party preference voters.)

California, along with all but two other states, is a winner-takes-all primary election for president, with the top vote-getter in each party securing all of the delegates.

For all statewide offices, state legislative offices, and U.S. congressional seats, only the top two vote-getters in the primary election – regardless of party preference - move on to the general election.

To change your party registration, you’ll need to re-register to vote. While the last day to register online for the primary was Feb. 20, you can't complete same-day voter registration and request your ballot in person at your county elections office or a voting center.

CalMatters contributed to this report.