The U.S. Supreme Court declined on Monday to let the U.S. Postal Service enforce a rule targeting mail-in ballots, dealing a setback to President Donald Trump’s effort to restrict voting by mail ahead of November’s midterm elections that will determine control of Congress.

The justices denied the Justice Department’s request to lift a ruling by Boston-based U.S. District Judge Indira Talwani that blocked the Postal Service from enforcing the measure while legal challenges by states and voting-rights groups proceed. The agency adopted the measure after Trump issued a March executive order aimed at tightening rules governing mail voting.c

Justice Samuel Alito, joined by fellow conservative Justice Clarence Thomas, dissented from Monday’s decision, writing that the Trump administration “is likely to succeed on the merits of its appeal.”

Trump’s fellow Republicans are locked in a tight battle to retain control of Congress in the midterms. Restricting mail-in ballots would stand to benefit Republicans given that Democratic voters disproportionately use mail-in ballots, according to various surveys.

Another federal judge, Washington, D.C.-based U.S. District Judge Carl Nichols, also ruled against the new rule on Sunday.

Under the new rule, states must provide lists of mail ballot recipients to the Postal Service and use agency-approved outbound and return ballot mail envelopes outfitted with unique barcodes. The Postal Service could then refuse to send out ballots that do not comply with the new standards or are associated with voters who do not appear on the lists.

Critics have said the plan could disrupt the delivery of thousands of legitimate ballots as the November 3 vote approaches and cause chaos given imminent plans by many states to send out mail ballots to eligible voters. The administration has said the new rule will prevent voter fraud, though evidence of such fraud is rare.

Trump signed his executive order targeting mail-in ballots after years of casting doubt on their security, though he often votes by mail himself. Trump has made false claims of widespread fraud in U.S. elections including his 2020 loss to former Democratic President Joe Biden.

The administration in a September 6 emergency request urged the Supreme Court to allow it to implement an “important federal policy to protect the mails from being used to commit voter fraud.”

A coalition of states, most of them Democratic-governed, and Washington, D.C., as well as a number of voting rights groups, challenged the new USPS rule.

Talwani imposed an injunction on September 4 blocking the rule, finding that it likely violated the U.S. Constitution, under which states administer elections. Talwani also said it would be impossible for the states to comply given the rapidly approaching midterms.

The Boston-based 1st U.S. Circuit Court of Appeals refused last Thursday to put Talwani’s order on hold. The 1st Circuit said that the rule “will likely result in the disenfranchisement of millions of voters across the country while providing minimal — if any — gains in combating voter fraud.”

Nichols granted a request from the Democratic Party and ​groups including the NAACP for a preliminary injunction blocking the rule. Nichols wrote that the rule could make it harder for some people to vote by mail and that it exceeded the Postal Service’s authority.

“No statute grants ​the Postal Service the power to issue key parts of the rule,” Nichols wrote.

All 50 states allow for some form of mail-in voting. Of those, 29 states allow voters to ask to cast ballots by mail without providing a reason, and eight conduct ​their elections entirely by mail.

The battle over mail ballots is one in a series of efforts by the administration to boost federal involvement in voting ahead of the midterms. On August 24, the Supreme Court lifted an earlier injunction imposed by Talwani in June blocking Trump’s executive order, including the USPS rule before it had been finalized.

(Reporting by Andrew Chung in New York; Editing by Will Dunham)