• The U.S. Supreme Court is reviewing Mississippi's law on mail-in ballot deadlines.
• Arguments from the Republican National Committee challenge late ballot acceptance.
• States like California rely on mail-in ballots with grace periods for counting.
• The decision may impact mail voting rules nationwide ahead of midterm elections.
• Concerns over election integrity and potential fraud were discussed during hearings.

On March 23, the U.S. Supreme Court began hearing a significant case concerning the counting of mail-in ballots that arrive after Election Day, but are postmarked on or before that date. The case centers on a Mississippi law that permits ballots to be counted if they are received within five days post-Election Day. This law, supported by the Republican Party, is challenged by various plaintiffs, including the Republican National Committee, who argue it conflicts with federal statutes mandating that ballots must be received by Election Day, according to Reuters and CBS News.

During the hearings, the Supreme Court's Republican-appointed justices expressed a leaning towards ruling that federal law requires all ballots to be in possession of election officials by Election Day. This could lead to significant changes in ballot acceptance policies in multiple states, many of which currently allow postmarked ballots to be counted if they arrive a few days late. California, for example, counts mail-in ballots that arrive within seven days after Election Day, and in 2024, over 406,000 such ballots were counted, representing about 2.5% of total votes cast, as reported by Los Angeles Times and CBS News.

Within the context of this case, former President Donald Trump's administration has advocated for policies to limit mail-in voting, claiming that it opens the door to electoral fraud, despite experts stating that incidents of voter fraud are exceedingly rare. Justice Samuel Alito commented on the potential for ballots arriving late to "flip the outcome" of elections, a point that raises concerns about maintaining election integrity, according to Reuters and Los Angeles Times.

As the Supreme Court weighs this case, known as Watson vs. Republican National Committee, election officials express concerns about how such a ruling could affect states that rely on mail voting, particularly impacting military members and overseas voters who often depend on grace periods for their ballots. The upcoming decision is critical, as it may come just months before the November midterm elections and could alter voting regulations across the country, as noted by CBS News and Los Angeles Times.