The Supreme Court agreed Monday to hear a challenge to Mississippi's practice of counting mail ballots that arrive after Election Day, a dispute that could scramble rules in dozens of states before the 2026 elections. In Watson v. Republican National Committee, the justices will weigh the meaning of Election Day. The RNC says late-arriving ballots undermine election integrity and public trust; Mississippi says Congress set the day voters must choose, not delivery deadlines, defending a short grace period similar to policies in many states.

Prepared by Lauren Mitchell and reviewed by editorial team.