WASHINGTON (AP) — The Supreme Court is hearing arguments Monday in a case from Mississippi over whether states can count late-arriving mail ballots, a target of President Donald Trump.

The outcome of the case could affect voters in 14 states and the District of Columbia, which have grace periods for ballots cast by mail, provided they are postmarked by Election Day. An additional 15 states that have more forgiving deadlines for ballots from military and overseas voters also could be impacted.

A ruling is expected by late June, early enough to govern the counting of ballots in the 2026 midterm congressional elections.

Forcing states to change their practices just a few months before the election risks “confusion and disenfranchisement,” especially in places that have had relaxed deadlines for years, state and big-city election officials told the court in a written filing.

California, Texas, New York and Illinois are among the states with post-Election Day deadlines. Rural Alaska, with its vast distances and often unpredictable weather, also counts late-arriving ballots.

Lawyers for the Republican and Libertarian parties, as well as Trump’s administration, are asking the justices to affirm an appellate ruling that struck down a Mississippi law allowing ballots to be counted if they arrive within five business days of the election and are postmarked by Election Day.

The court challenge is part of Trump’s broader attack on most mail balloting, which he has said breeds fraud despite strong evidence to the contrary and years of experience in numerous states.

Last year, the Republican president signed an executive order on elections that aims to require votes to be “cast and received” by Election Day. The order has been blocked in pending court challenges.

At the same time, four Republican-dominated states — Ohio, Kansas, North Dakota and Utah — eliminated grace periods last year, according to the National Conference of State Legislatures and Voting Rights Lab.

The issue at the Supreme Court is whether federal law sets a single Election Day that requires ballots to be both cast by voters and received by state officials.

In striking down Mississippi’s grace period, Judge Andrew Oldham of the 5th U.S. Circuit Court of Appeals wrote that the state law allowing the late-arriving ballots to be counted violated federal law.

Oldham and the other two judges who joined the unanimous ruling, James Ho and Stuart Kyle Duncan, all were appointed by Trump during his first term.

Mark Sherman, The Associated Press