The Justice Department says a U.S. Postal Service letter carrier in Utah threw out more than 300 mail ballots that were being sent to voters for the state's June primary.
The Justice Department asked the Supreme Court to intervene in an ongoing legal battle over U.S. Postal Service rules for mail ballots just weeks before the November midterm elections.
The whistleblower, described by lawyers as a federal official, disclosed information about the Postal Service's new mail-voting procedures to Democratic Sen. Richard Blumenthal of Connecticut.
President Trump signed an executive order in March requiring the creation of a list of U.S. citizens eligible to vote in each state and imposing stricter mail-in ballot rules.