A coalition of election integrity groups has filed an amicus brief urging the Supreme Court to uphold a lower court ruling that would require mail-in ballots to be received by Election Day, not merely postmarked by that date. The case, Watson v. Republican National Committee, could have far-reaching implications for voting procedures across the country.

The conservative-leaning groups, including the Honest Elections Project and the Center for Election Confidence, are supporting the Republican National Committee’s challenge to Mississippi’s postmark deadline. Mississippi currently counts mail ballots received up to five business days after Election Day if they are postmarked by Election Day itself.

“Counting ballots that are received after Election Day unnecessarily damages public trust in election outcomes, delays results, and violates the law,” said Jason Snead, Honest Elections Project executive director, in a statement.

At the heart of the case is a fundamental question about federal election law: Does the statute establishing a single national Election Day require all ballots to be in the hands of election officials by the time polls close? The 5th Circuit Court of Appeals previously ruled in favor of the RNC, finding that federal law supersedes Mississippi’s extended deadline.

The Supreme Court is scheduled to hear oral arguments on March 23, with a decision expected by summer. The outcome could invalidate similar postmark-based deadlines currently in place in 14 states and Washington, D.C. Since the 2024 midterms, four Republican-controlled states – Kansas, Ohio, Utah and North Dakota – have already moved to require receipt by Election Day.

The election integrity groups argue that under the Supreme Court’s decision from three decades ago in Foster v. Love, the “final act of selection” must occur on Election Day itself. They interpret the receipt of a mail-in ballot as the act of casting a ballot, which by this standard cannot happen after Election Day.

Proponents of the stricter deadline claim it would establish a clearer standard for ballot acceptance and enhance public confidence in election results. They also noted that recent U.S. Postal Service guidance has warned that postmarks might not reliably reflect when a ballot actually entered the mail system.

“A favorable ruling would protect the rights of voters and the integrity of the democratic process, and ensure that it is easy to vote but hard to cheat in future elections,” Snead added.

However, the coalition acknowledged that even if the Supreme Court affirms the lower court ruling, election officials would still be tabulating ballots beyond Election Day in close races. The distinction is that all ballots would need to be received by officials before polls close, not merely postmarked by that time.

The case represents a significant test of federal authority over state election procedures. The RNC strategically chose to bring the case in the U.S. Circuit Court of Appeals for the 5th Circuit, which is known for its conservative leanings.

If the Supreme Court upholds the 5th Circuit’s ruling, states would need to adjust their mail-in ballot procedures ahead of the 2026 midterm elections. Military and overseas ballots, which are governed by the separate Uniformed and Overseas Citizens Absentee Voting Act, would likely remain unaffected by the decision.

The dispute highlights ongoing tensions over election administration in the United States, as states continue to refine voting procedures following the significant expansion of mail-in voting during the COVID-19 pandemic. The Supreme Court’s ruling could provide clarity on one aspect of election administration that has varied widely across states.