California Vote-By-Mail Faces Legal, Political Challenges From Trump Allies

[This column was reported for Political Breakdown, a bi-monthly newsletter offering analysis and context on Bay Area and California political news. Click here to subscribe.]

California’s expansive system of vote-by-mail is facing a two-pronged attack driven by President Donald Trump’s spurious attempts – without evidence – to discredit mail voting as electoral cheating.

At the local level, Riverside County Sheriff Chad Bianco, a Republican running for governor, has seized all ballots cast within his county during the November 2025 election to conduct what he calls an investigation into potential fraud.

Conservative justices on the Supreme Court also raised the specter of potential fraud this week as they questioned a Mississippi law, similar to one in California, that allows ballots postmarked by Election Day to be received and counted up to five days later.

Jenny Farrell, the executive director of the League of Women Voters of California, told me that taken together, the developments are part of “a growing pattern of actions both in California and nationally that risk undermining public confidence in our elections.”

Bianco’s office seized roughly 1,000 boxes – about 650,000 ballots – from the Riverside County Registrar of Voters in late February.

His reasoning: A citizens group called the Riverside Election Integrity Team, said their audit of ballot intake forms found just 611,426 ballots — 45,896 short of the county’s final count of 657,322 votes. The local group claimed officials overstated the tally in an election where California voters overwhelmingly approved Proposition 50, a Democratic redistricting plan.

“The investigation is going to determine what the discrepancy is,” Bianco said at a news conference Friday. “Is it human error? Is it machine error?”

But in a presentation to the Riverside County Board of Supervisors in February, Registrar of Voters Art Tinoco said the ballot intake forms, filled out by hand by volunteers at voting locations, were not a reliable source to compare to the final vote count — which takes place after a machine scan of ballots at county offices.

“These are completed in the field by election officers during long work days — let’s keep that in mind, folks get tired,” Tinoco said. “It’s very possible that the staff may not have recorded the numbers accurately on these daily mail intake forms.”

County supervisors vowed to look further into the ballot intake forms. But Bianco’s move to seize the ballots was “unprecedented,” said Matt Barreto, faculty director of the UCLA Voting Rights Project.

“The single most important thing is having transparency and trust in the counting of the ballots,” Barreto said. “In no election should law enforcement officials be seizing ballots, removing them from the county and doing a private and separate count.”

After all, Bianco is a leading candidate for governor in the state’s June 2 primary. Any move to align himself with Trump’s crusade against mail voting could help Bianco overtake his Republican rival in the race, commentator Steve Hilton.

“He’s certainly pursuing it only for publicity, not for election integrity,” Barreto said — a charge Bianco denied at his press conference.

In a lawsuit filed Monday, California Attorney Rob Bonta asked the state’s 4th District Court of Appeal to freeze Bianco’s investigation and halt a new count of ballots.

“The Sheriff has not identified any particular crime that may have been committed by anyone — a necessary predicate to obtain a criminal search warrant,” Bonta’s office said in a statement. “By all appearances, this investigation is little more than a fishing expedition meant to sow distrust and undermine public confidence in our elections.”

But a three-judge panel on the appeals court denied Bonta’s petition on Tuesday and instructed the attorney general to file his suit with a lower court instead.

No one appears more determined to discredit vote-by-mail than Trump, who this week said, “mail-in voting means mail-in cheating.”

Trump and Republicans in Congress are advocating for the SAVE Act, which would ban states such as California from automatically mailing all voters a ballot and instead require voters to submit an application and show proof-of-citizenship documents in order to receive a mail ballot.

While that bill faces uncertain prospects of clearing the Senate, the U.S. Supreme Court could soon block states from counting ballots that arrive by mail after Election Day. In California, ballots postmarked by Election Day can be counted if they are received up to one week later.

During oral arguments Monday in Watson v. National Republican Committee, a challenge to Mississippi’s voting rules, conservative Justices Brett Kavanaugh and Samuel Alito raised concern that significant changes in results in the days and weeks after Election Day — a common occurrence in closely-contested California races — could undermine public confidence in elections.

“Some of the briefs have argued that confidence in election outcomes can be seriously undermined if the apparent outcome of the election on the day after the polls close is radically flipped by the acceptance later of a big stash of ballots that flip the election,” Alito said.

In reality, a relatively small number of ballots arrive days after the election in California, said Cathy Darling Allen, the former registrar of voters in Shasta County. The real slowdown comes from the sheer volume of ballots that arrive on Election Day, she said, with each requiring election workers to conduct a signature match before it can be counted.

To speed up the count, Darling Allen said, counties need money for more election workers — and larger facilities for ballots and machines. “We need more space, not only to store ballots after elections, but also to process them,” she said.

A decision to limit the ballot-arrival window is only likely to add more headaches in the June 2 primary, Darling Allen said.

A decision in the Watson case is expected in late June, right as California must certify its June primary results.

“What does that mean for the ballots that were received on June 3rd or 4th or 5th in California?” Darling Allen said. “Are registrars going to have to segregate those ballots? Do they not even open the envelopes until the Supreme Court rules?

“That’s what I’m worried about.”