Supreme Court Ruling Due June 30 on Mail-In Ballots: 5-Day Grace Period at Risk

For election law practitioners and state legislators, the impending Supreme Court decision in Watson v. RNC is more than a single-state dispute—it’s a constitutional reckoning that could redefine the boundaries of state autonomy in election administration. With a majority of justices signaling a strict textualist reading of federal election statutes, the ruling may force Washington and other vote-by-mail states to overhaul ballot receipt rules, while simultaneously testing the limits of executive authority in an era of heightened voting rights litigation.

The U.S. Supreme Court is on the cusp of a decision that could fundamentally alter vote-by-mail procedures across the country. By Tuesday, June 30, 2026—the final day of its current term—the Court is expected to rule in Watson v. Republican National Committee, a case challenging Mississippi’s law that allows ballots postmarked by Election Day to be counted if received within five days thereafter. For states like Washington, which relies entirely on mail-in voting, the implications are seismic: if the justices, as observers suspect, adopt a strict interpretation of “Election Day” under federal law, post-election receipt windows would be nullified, forcing ballots to physically arrive by the close of polls. This would not only upend Washington’s long-standing electoral infrastructure but also reverberate across other states with similar grace periods.

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Republican National Committee, a case challenging Mississippi’s law that allows ballots postmarked by Election Day to be counted if received within five days thereafter.

The case originated when the Republican National Committee and other plaintiffs argued that Mississippi’s five-day acceptance window violates the uniformity of Election Day as defined by the Elections Clause and federal statutes. During oral arguments in March 2026, several justices appeared sympathetic to a textualist approach, questioning whether Congress ever intended to allow states to extend the counting period beyond a single 24-hour day. A ruling in favor of the plaintiffs would mandate that all federal elections adhere to a bright-line arrival deadline, regardless of when a ballot was mailed. For Washington, which currently counts ballots postmarked by Election Day and received up to two weeks later (state law allows a longer period for state races, but federal law’s supremacy could override it), this would require immediate legislative adjustments before the upcoming midterm elections.

Simultaneously, a second legal front threatens mail-in voting: a multistate lawsuit against President Donald Trump’s executive order directing the U.S. Postal Service to withhold delivery of mail-in ballots to voters in states that do not share voter registration rolls with the federal government. That order has been stayed by a federal court pending further litigation, but it underscores the administration’s aggressive posture toward voting procedures it disfavors. The confluence of these cases paints a portrait of an electoral system at a crossroads, where judicial interpretation of federal authority will define the contours of ballot access in an era of deep political polarization.

For election law practitioners, the Watson ruling stands as the most significant since the Supreme Court’s 2013 Shelby County decision gutted preclearance requirements of the Voting Rights Act. A strict ruling could dismantle mail-in voting systems that have expanded dramatically over the past decade, in part because they were widely adopted during the COVID-19 pandemic. The Court’s reasoning will likely scrutinize the constitutional balance between states’ rights to administer elections and Congress’ power to override those choices under the Elections Clause. A broad holding could invite further federal preemption challenges, possibly even on issues like ballot design or signature verification, fundamentally reshuffling state-federal roles. Meanwhile, the executive order case, though currently stayed, tests the boundaries of presidential authority in election administration—an area historically left to states and Congress. If the stay is lifted, it could disrupt ballot delivery chains, disproportionately affecting vulnerable populations who rely on mail-in voting.

Washington officials are already bracing for the fallout. The Secretary of State’s office may need to launch an emergency rulemaking or seek legislative changes to compress the ballot return timetable, which would also impact ballot processing, voter education, and postmark reliability. The state’s reliance on the USPS raises concerns about whether mail service speeds can reliably meet an Election Day deadline, especially in rural areas. If Trump’s executive order is ever enforced—requiring the USPS to essentially blacklist states over voter roll disputes—it could disenfranchise entire electorates, raising serious due process and constitutional questions.