How a coming Supreme Court decision on mail-in ballot ruling could impact California

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The Supreme Court is set to decide as soon as this week whether states can accept mail-in ballots that arrive after election day in a case that could invalidate the so-called grace period in places like California.

The decision will come after enormous attention was paid across the country to the results in both the California governor’s contest and the battle for mayor of Los Angeles, where Republican candidate Spencer Pratt was overtaken by progressive candidate Nithya Raman, drawing outrage from President Trump and others on the right.

In California, the coming Supreme Court decision would likely have no bearing on those races because they are state and local and not federal contests. But it could have consequences for U.S. House races in the fall.

At the center of the judicial debate is a Mississippi law that allows mail-in ballots to be counted so long as they are postmarked by when polls close and received by election officials within five days afterward. More than a dozen other states and Washington, D.C., have similar rules, though deadlines differ.

Challengers, including the Republican National Committee, argue Mississippi’s ballot deadline is preempted by a federal law that sets the Tuesday after the first Monday in November as Election Day for federal offices.

The Supreme Court seemed poised to limit mail-in ballots after hearing oral arguments in late March, a ruling that could force the Golden State and others to change their vote-counting rules just months before the midterm elections.

“That could create a crunch for states like California and some of the other vote by mail states,” said Geoffrey Skelley, Decision Desk HQ’s chief elections analyst. “It’s because the Supreme Court might say with immediate effect ‘you can’t do this anymore.’”

California was one of multiple states that adopted universal mail-in voting following the COVID-19 pandemic, meaning that each of the state’s roughly 23 million registered voters automatically receives a vote-by-mail ballot for upcoming elections.

Those ballots are accepted so long as they are dropped at secure locations received by elections offices by 8 p.m. local time on election day or postmarked by that date and returned by the following Tuesday, according to state law.

The extended deadline and other administrative requirements mean it can take days or weeks to finalize the tallies of any given election — a process state officials argue is slowed further by the sheer volume of incoming ballots.

An estimated 1.6 million mail-in ballots for the June 2 primaries had yet to be processed by county election officials as of Monday, according to the California secretary of state’s office.

The rules surrounding mail-in voting have made blue states like California prime targets for criticism from Republicans and the Trump administration, which is actively trying to restrict the practice over unsubstantiated claims of fraud.

Trump criticized the California process in the mayoral and gubernatorial races in a testy interview Sunday.

“It’s four days and they aren’t even close to coming up with the — do you know why they’re doing that? Because they’re cheating on the election,” President Trump claimed during an interview with NBC’s “Meet the Press” on Sunday, without providing any evidence.

Fraud concerns underpinned an argument made by several conservative groups for why the Supreme Court should affirm the 5th Circuit’s decision striking down Mississippi’s five-day window.

“The longer the period over which the election is conducted, the greater the opportunity for and risk of fraud,” lawyers for Citizens United and others wrote in a February amicus brief. “Nevertheless, some states are determined to extend election day, both before and after, transforming a day into a election season, providing numerous opportunities for all manner of election manipulation.”

Opponents argue restricting mail-in ballots risks disenfranchising millions of potential voters, including military members and U.S. citizens residing overseas. Twenty-nine states and D.C. accept at least some military and overseas ballots after election day, according to the National Conference of State Legislatures.

“Military and overseas voters frequently can’t control when the postal service or the military mail systems deliver their ballots, and if ballots mailed on time are discarded simply because they arrive after election day, service members could lose their right to vote through no fault of their own,” Janessa Goldbeck, the CEO of Voice Vet Foundation, told The Hill. The organization intervened in the case in support of Mississippi.

Even if the court declares the grace period unconstitutional, election experts say it may not dramatically alter the number of ballots that are accepted or rejected.

A February analysis by VoteBeat found that roughly 373,000 California ballots in the 2024 general election arrived after Election Day with valid postmarks, only about 2.3 percent of the state’s total vote.

The court could invalidate the grace periods while still leaving them intact for November under a doctrine known as the Purcell principle, which holds that federal courts should avoid changing the rules shortly before an election to prevent voter confusion.

A broad ruling applying to all states could also create the possibility of split deadlines, wherein ballots for local and statewide elections may be accepted if postmarked by election day but ballots for federal elections would not count.

“My prediction would be that in practice if the Supreme Court issued a ruling that applied to federal races, most states would choose to align their laws to get rid of the grace period for all races, rather than have a bifurcated system,” Adler said.

Adler said that while it may be difficult to predict the partisan consequences, it could create an undue burden on already-strained election officials.

“There’s some jurisdictions where mostly Democrats vote by mail, and there’s some where more Republicans vote by mail, so that the actual outcome is hard to predict,” he said. “But if the change is made late, I can definitely predict that there would be voter confusion and a lot of stress on election officials to make sure that those changes are communicated properly.”

Ryan Mancini contributed.

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