A federal judge nominated by President Donald Trump blocked a new Postal Service rule governing mail-in ballots, creating a second legal obstacle for the policy as the administration asks the Supreme Court to let it take effect before the Nov. 3 midterm elections.

U.S. District Judge Carl Nichols granted Democratic and voting rights groups a preliminary injunction late Sunday, concluding they were likely to prove that central parts of the rule exceeded the authority Congress granted to the Postal Service.