A Democratic senator on Tuesday released whistleblower allegations that the U.S. Postal Service has botched implementation of Trump-favored restrictions on mail-in ballots, heightening uncertainty as the administration defends the rule in court. Attorneys for an anonymous whistleblower told Senator Richard Blumenthal that a rushed federal screening system—requiring states to submit voter names, addresses and ballot barcodes—could delay or block delivery of millions of ballots before the November midterms. A federal judge has temporarily blocked the finalized rule for two weeks, with a hearing and separate appeals underway, and the fight could return to the Supreme Court within days or weeks. Mail-in voting is used by one in three Americans, so any disruption would reach a large share of the electorate. Under the rule, postal workers would return ballots lacking required clearance, and a reported zero-percent barcode failure standard could reject an entire batch if one code fails to scan. Election officials and voting-rights groups warn the rollout could create severe administrative and technology problems, especially in rural areas and for voters who depend on mail ballots.