WASHINGTON — The Supreme Court on Monday refused to allow President Donald Trump’s proposed restrictions on mail voting to take effect before the 2026 midterm elections, leaving states to continue using the procedures already in place. The brief order came as voting preparations were already underway and several states had begun sending ballots to voters. Alabama, North Carolina and Wisconsin started mailing ballots over the past week, even though the administration’s proposed system was not operational. The plan would have required states to use a standardized ballot envelope and upload lists of eligible voters to a federal online portal. Under the proposal, the U.S. Postal Service could have declined to deliver ballots from states that did not comply. Election officials warned that implementing a new system so close to the election would be unworkable. A whistleblower report also raised concerns that problems with the portal could prevent millions of ballots from being sent. The report said a single barcode error could cause an entire batch of ballots to be rejected. Democratic state officials and voting-rights organizations challenged the restrictions in court, arguing that the president lacked constitutional authority to impose new election rules and that the changes could effectively eliminate mail voting shortly before a major election. Lower courts blocked the administration’s plan, including through a preliminary injunction issued by a judge nominated by Trump. The administration argued that federal control over the Postal Service gave it authority to establish mail-ballot handling requirements and that states could comply in time. The Supreme Court previously issued a procedural ruling favorable to the federal government but did not decide whether the restrictions were lawful. Justices Samuel Alito and Clarence Thomas dissented from Monday’s order. Justice Brett Kavanaugh agreed that the restrictions should not apply during the midterms but signaled that he could ultimately side with the administration on the legality of the plan. The ruling has national significance because nearly one-third of voters cast ballots by mail. Trump has repeatedly attacked mail voting and falsely blamed it for his 2020 loss to Democrat Joe Biden, despite having used mail voting himself, including this year. For now, voters and election officials can rely on the mail-ballot systems already established by their states. The Supreme Court’s decision does not end the broader legal dispute, leaving the possibility of another ruling after the midterm election process is complete.