Over the past two decades, the Supreme Court has steadily eroded access to the ballot. By striking down key provisions of the Voting Rights Act, upholding strict voter ID laws, and enabling large-scale voter roll purges, the Court has made it harder for Americans to vote – a trend that poses a grave threat to the democratic process.

This Term, the Court is considering yet another effort to roll back voting access in Watson v. Republican National Committee. This case arises out of the Fifth Circuit, where a three-judge panel struck down a Mississippi law that allows election officials to count ballots postmarked by Election Day but received up to five business days later. The law ensures that voters who cast their ballot on time are not disenfranchised due to postal delays or delivery complications that occur through no fault of their own. But the stakes extend far beyond Mississippi’s borders: at least 29 states and D.C. have similar statutes accepting mail-in ballots received shortly after Election Day.

The Supreme Court now has the opportunity to correct the Fifth Circuit’s mistake. In a brief filed earlier this year, the Constitutional Accountability Center explains why both history and federal election law make clear that states may count timely cast ballots received after Election Day.

Although absentee voting gained renewed attention during the COVID-19 pandemic, the practice is far from a modern innovation. Its roots stretch back to the early Republic, with documented instances as early as 1775 in New Hampshire and 1813 in Pennsylvania. The first example of widespread usage, however, occurred during the Civil War, when lawmakers recognized that soldiers needed mechanisms to vote while serving away from home lest they lose their right to participate in the democratic process.

From 1861 to 1865, state laws and constitutional amendments permitting soldiers to vote swept across Union and Confederate states alike. By the war’s end, nineteen Union states and seven Confederate states had some form of absentee voting for soldiers. In the 1864 election alone, soldiers cast an estimated 230,000 to 235,000 ballots, accounting for roughly 7.5% of the total vote in states that permitted soldier voting. These measures reflected a broad consensus that the right to vote must endure even under the extraordinary conditions of wartime.

Despite this robust history, the Republican National Committee—the party challenging Mississippi’s law—insists that history and tradition supports the position that ballots must be received by Election Day. It claims that Civil War-era history “only reinforces the necessity of election-day receipt.” In reversing the district court’s decision, the Fifth Circuit similarly concluded that “historical practice confirm this ‘day for the election’ is the day by which ballots must be both cast by voters and received by state officials.” But this argument ignores that there were multiple models of absentee voting during the Civil War, and under one of these models, ballots were clearly received after Election Day—by design.

There were in fact three primary methods adopted by the states to facilitate soldier voting. First, several states used proxy-style voting systems that resembled modern absentee voting. This method required soldiers to mark their ballots in camp and mail them home to be cast alongside civilian votes. Second, several states dispatched election officials to military barracks, allowing soldiers to cast ballots on-site in portable ballot boxes. Third, a number of states—including Rhode Island, Nevada, and Pennsylvania—permitted unit-level voting. Under this model, soldiers cast votes on Election Day under the supervision of commanding officers who then forwarded the ballots or voting tallies to local election authorities for certification and counting. These commanding officers were not formally deputized as election officials and were chosen solely for their military rank. By design, it was understood that ballots would arrive after Election Day, thus requiring states to enact explicit grace periods to accommodate the time it would take for ballots to travel from the military camps.

Notably, the text of many state laws at the time made clear that states understood Election Day as the day votes were cast, and that it was permissible for receipt to occur thereafter. The 1864 Maryland Constitution, for example, stated that the Governor must “wait for fifteen days after the day on which the State vote is taken, so as to allow the returns of the soldiers’ vote to be made before the result of the whole vote is announced.” Similarly, an 1861 Georgia statute allowed for votes to be counted so long as they arrived to “the executive department fifteen days after the day of the election.” In each of these examples, state law clearly allowed for votes to be received and counted well after Election Day, provided that they arrived within a statutorily defined period.

This historical tradition reflects the fact that, while federal law establishes Election Day as the day voters choose their preferred candidates, states possess broad authority to regulate the electoral process to ensure that all votes cast are properly counted.  As this history shows, nothing in federal law prevents states from setting reasonable post-Election Day deadlines for ballot receipt. Mississippi’s law, which allows officials to count ballots received within five business days after the election, falls squarely within this tradition.

If the Supreme Court upholds the Fifth Circuit’s decision, it will turn a blind eye to both the text of federal election law and longstanding historical practice. Such a ruling would harm voters who disproportionately rely on mail-in voting—namely older voters, individuals with disabilities, university students, and military servicemembers—and quiet the voices of countless citizens across the country.