The Supreme Court’s March 23 oral arguments in Watson v. Republican National Committee revealed a clear conservative majority skeptical of state laws permitting mail ballots postmarked by Election Day to be counted if received days later. Justices focused on federal statutes fixing Election Day as the deadline for both casting and receipt of ballots, questioning grace periods in Mississippi and more than a dozen other states. A decision expected by late June or early July could standardize receipt deadlines nationwide ahead of the 2026 midterms. Traders assign a 71 percent implied probability to a ruling barring post-Election Day counting, reflecting the arguments’ trajectory and historical patterns of the Court applying strict statutory interpretations to federal election timing.