WASHINGTON — The Supreme Court on Monday rejected the Trump administration’s request to let the U.S. Postal Service enforce new requirements for delivering mail-in ballots ahead of the 2026 midterm elections. The justices’ decision leaves intact a lower-court ruling that barred the Postal Service from putting the requirements into effect in the coming weeks. The lower court had found that the changes could disrupt election administration and potentially prevent millions of voters from having their ballots delivered. The Supreme Court acted on its emergency docket, issuing only a brief explanation from the majority. The justices said the administration’s position was unlikely to succeed, without providing a detailed legal analysis. Justice Brett Kavanaugh wrote separately to explain his agreement with the result. He said state and local election officials did not have enough time to reasonably carry out the new rules before the election. The ruling prevents the administration from imposing the delivery requirements on an accelerated timetable as election officials prepare for the midterms. Mail voting procedures are generally administered by state and local governments, making changes to postal delivery standards especially consequential for voters who depend on ballots arriving by mail. The decision also underscores the stakes of late changes to election procedures. With ballots moving through local election systems and the Postal Service on different schedules, officials have warned that new requirements introduced close to an election could create confusion, delays and unequal burdens for voters.