The Supreme Court could decide as soon as this week whether states may continue accepting mail-in ballots that arrive after Election Day, a ruling that would land hardest in California, where the state mails ballots to roughly 23 million registered voters and routinely counts hundreds of thousands that trickle in days after polls close.
The case centers on a Mississippi law that allows mail-in ballots to be counted if they are postmarked by the time polls close and received by election officials within five business days afterward. The Republican National Committee and other challengers argue the law is preempted by a federal statute that designates the Tuesday after the first Monday in November as Election Day for federal offices. The Fifth Circuit agreed, striking down Mississippi's five-day window.
Now the justices must decide whether to uphold that reasoning, and if they do, more than a dozen other states and Washington, D.C., with similar post-Election Day receipt deadlines could be forced to rewrite their rules before voters head to the polls again this fall.
No state stands to feel the impact more than California. Since adopting universal mail-in voting after the COVID-19 pandemic, the Golden State automatically sends a ballot to every one of its roughly 23 million registered voters. Under current law, ballots dropped at secure locations must reach elections offices by 8 p.m. local time on Election Day. Ballots sent through the mail need only be postmarked by Election Day and can arrive as late as the following Tuesday.
That window matters. A February analysis by VoteBeat found that roughly 373,000 California ballots in the 2024 general election arrived after Election Day with valid postmarks, about 2.3 percent of the state's total vote. In a close House race, 2.3 percent is not a rounding error. It is the margin between winning and losing.
The scale of California's mail-ballot operation was on display again this month. The Hill reported that the California secretary of state's office said an estimated 1.6 million mail-in ballots from the June 2 primaries had yet to be processed by county election officials as of Monday. That backlog illustrates how deeply the state's election infrastructure depends on extended counting timelines.
The legal argument is straightforward. Federal law sets a single Election Day for federal offices. Challengers say that means votes must be received, not merely postmarked, by that date. Allowing ballots to drift in for days afterward, they contend, stretches "Election Day" into an election week and opens the door to manipulation.
Lawyers for Citizens United and others made that case bluntly in a February amicus brief urging the Supreme Court to affirm the Fifth Circuit's decision:
"The longer the period over which the election is conducted, the greater the opportunity for and risk of fraud."
The brief went further:
"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."
President Trump weighed in during an NBC "Meet the Press" interview on Sunday, criticizing California's drawn-out counting process in the context of the Los Angeles mayoral and gubernatorial races. Republican candidate Spencer Pratt was overtaken by progressive candidate Nithya Raman in the battle for mayor of Los Angeles, a reversal that unfolded as late-arriving ballots were tallied.
"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."
Opponents of eliminating post-Election Day receipt windows raise one concern that deserves serious attention: military and overseas voters. Twenty-nine states and D.C. currently accept at least some military and overseas ballots after Election Day, according to the National Conference of State Legislatures.
Janessa Goldbeck, CEO of the Voice Vet Foundation, which intervened in the case in support of Mississippi, told The Hill that service members could lose their franchise through no fault of their own if timely mailed ballots are thrown out for arriving late.
"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."
That is a legitimate concern, and any legislative fix should account for it. But the existence of a hard case for deployed troops does not justify a blanket policy that lets millions of domestic ballots roll in days after an election has supposedly ended. Congress can protect military voters with targeted legislation. It does not need to leave the entire system open-ended to do so.
Geoffrey Skelley, Decision Desk HQ's chief elections analyst, warned that a ruling with immediate effect could create logistical problems for states built around extended mail-ballot timelines.
"That could create a crunch for states like California and some of the other vote by mail states."
"It's because the Supreme Court might say with immediate effect 'you can't do this anymore.'"
An analyst identified only as Adler predicted that most states would respond by eliminating grace periods across the board rather than running two different systems, one for federal races, one for state and local contests.
"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 also cautioned that the partisan effects are harder to predict than either side assumes.
"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."
But Adler added that late changes would generate confusion regardless of party:
"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."
Even if the justices rule against post-Election Day receipt windows, the practical timeline is uncertain. The Purcell principle, the doctrine that federal courts should avoid changing election rules shortly before an election to prevent voter confusion, could delay enforcement. Under that reasoning, grace periods might remain intact through November while states scramble to rewrite their laws for future cycles.
But the decision could still reshape the landscape for U.S. House races this fall if the Court issues a clear mandate and states move quickly. California's midterm contests, in particular, could look very different if 373,000 late-arriving ballots, or whatever the 2026 equivalent turns out to be, are no longer part of the count.
Strip away the legal jargon and the case comes down to a simple proposition: Does "Election Day" mean Election Day? Federal law says there is one day on which Americans choose their representatives. Some states have turned that day into a suggestion, a postmark deadline followed by an open-ended receiving period during which the outcome of races can shift as new ballots materialize.
The Supreme Court heard oral arguments in late March. A decision could arrive any day. However the justices rule, the case has already exposed a fundamental tension that state legislatures have been content to ignore: you cannot run a system in which every registered voter automatically receives a mail ballot, allow those ballots to arrive days after the election, and then act surprised when the public questions the integrity of the count.
Election Day is supposed to be the day the voters decide, not the day the counting begins.
