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The Supreme Court may be poised to commit the single biggest act of disenfranchisement in modern history in a direct assault on the constitutional authority of states to set election laws. During Monday’s arguments in Watson v. Republican National Committee, the conservative justices lined up to attack state laws permitting the counting of ballots that arrive shortly after Election Day if they were postmarked on time. About 30 states have enacted similar laws, and they have had a major impact on American elections: In 2024 alone, more than 750,000 late-arriving ballots were counted because of a state’s grace period. Now there is a very real chance that the Supreme Court will wipe out these laws in one fell swoop, causing chaos in the upcoming midterms that could disproportionately impact Democratic voters.

That news, in itself, is a five-alarm fire for democracy. But what makes it even more disturbing is the fact that so many justices proved eager to embrace a legal theory that is incoherent, dishonest, and rooted in paranoid hostility toward mail voting. The court’s right flank spent much of Monday’s arguments airing grievances about vote-by-mail’s supposed potential for fraud alongside partisan hostility toward lax ballot deadlines. Because there is so little evidence of said fraud, these justices warned of the threat of “appearance of fraud” as being just as dangerous—with little note about who the biggest purveyor of the false perception that fraud infests our elections is and what his real aims are. These justices concocted absurd hypotheticals seemingly designed to highlight the nation’s ostensible lack of election integrity. Yet they spent remarkably little time offering any legal justification for striking down democratically enacted laws that govern more than half the country. This court may not have endorsed Donald Trump’s big lie in 2020, as the president recently griped. But it could be on the brink of imposing one of his favored voter suppression policies by judicial decree.

Watson began when the Republican National Committee challenged a Mississippi law that directs election officials to count mail ballots postmarked by Election Day, as long as they arrive within five business days of Election Day. The RNC argued that Congress has preempted such laws through federal legislation, mostly passed in the 19th century, setting the date for federal elections. Just before the 2024 election, the far-right 5th U.S. Circuit Court of Appeals agreed, striking down the Mississippi statute. It asserted that the words “Election Day,” as used in the federal code, mean the date by which state officials must receive an eligible ballot. So federal law, according to the 5th Circuit, nullifies state statutes that seek to count any ballots that come in after that date. When the Supreme Court took up the case, the Trump administration sided with the 5th Circuit, urging the justices to strike down Mississippi’s statute and those like it.

The problem with this theory—as the liberal justices hammered throughout arguments—is that it has no basis in law, history, or precedent. “Election Day” has long been........

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