The Supreme Court is set to hear oral arguments Monday in a closely watched case that could reshape how millions of Americans vote, focusing on a deceptively simple question with sweeping implications: What counts as Election Day?
The case, Watson v. Republican National Committee, centers on whether states may count mail-in ballots that are postmarked by Election Day but arrive days later.
Backed by allies of President Donald Trump, the challenge could invalidate laws in at least 18 states and territories and potentially disqualify hundreds of thousands of ballots in upcoming elections.
At the heart of the dispute is a Mississippi law letting ballots be counted if they are postmarked by Election Day and received within five business days.
Similar grace periods exist across multiple states, as well as in jurisdictions such as Puerto Rico and Guam.
The Republican National Committee, a key plaintiff, argues that federal law establishes a single, uniform Election Day, meaning ballots must be received — not just sent — by that date.
In its complaint, the RNC contends that extended deadlines undermine election integrity and create opportunities for fraud.
Critics say the legal push stems from long-standing and unproven claims about widespread voter fraud in mail-in voting, allegations made by Trump following the 2020 presidential election.
Still, Republicans argue that ballots arriving after Election Day could raise concerns about chain-of-custody security, delays in verification, or the potential for tampering during transit.
Others cite the possibility of individuals trying to submit ballots on behalf of others or improperly harvesting ballots.
House Speaker Mike Johnson recently echoed these concerns, noting that some Republican candidates who led on Election Day later lost as mail ballots were counted.
"It looks on its face to be fraudulent," he said, though he acknowledged he could not prove wrongdoing.
In 2024, about 725,000 ballots nationwide were postmarked by Election Day but arrived within legally accepted windows.
In some states, these late-arriving ballots made up a small fraction of total votes but could influence close races.
The case also raises concerns about election administration, as changing rules close to an election can create confusion for voters and strain election systems.
The Supreme Court has previously cautioned against such disruptions through the "Purcell principle," which discourages last-minute judicial changes to election procedures.
Some Republicans argue that stricter deadlines would improve public confidence by speeding up vote counts.
A decision is expected later this year, just months before voters head to the polls in an election cycle that will determine control of Congress.
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