Roughly six weeks before the first midterm ballots are mailed out, the U.S. Postal Service is emerging as a pivotal player in an election season that will determine control of Congress.

President Donald Trump is seeking greater control over mail balloting through an executive order while a change to how the agency processes mail is leading to criticism that it’s failing to deliver ballots on time.

Democratic officials have raised concerns over the past week about how quickly the Postal Service will process ballots after tens of thousands of them in California and hundreds in Wisconsin arrived at local election offices too late to be counted in elections earlier this year. The top election offices in Kansas and Michigan are urging voters who want to cast their ballots early to avoid the mail and instead drop them off in person.

The Postal Service replied to those concerns Tuesday by saying it remains “committed to fulfilling our role in the electoral process.”

“We provide a secure, efficient, and effective way for citizens to participate when policymakers decide to use mail as part of their elections,” it said in a statement.

The Postal Service faced similar questions about mail delivery in 2024, but the scrutiny this year is heightened because of an executive order Trump issued in March that seeks to create a national voter list to guide the Postal Service in deciding who gets a mail ballot.

The order has sparked multiple lawsuits and federal court orders, leading to a case now before the U.S. Supreme Court in which the administration is asking the justices to allow it to impose its restrictions on mail balloting.

Trump has lied for years about voter fraud to try to explain away his loss to Democrat Joe Biden in 2020, and mail balloting is a favorite target, even though he has used the method himself. During a recent stop in Michigan, he falsely characterized mail balloting as “inherently corrupt” and added, “Hopefully there will be no mail-in ballots.”

A 2025 report from the research group Brookings identified about four cases of fraud for every 10 million mail ballots cast.

Despite Trump’s attacks, the method remains popular with voters of both major parties. In 2024, nearly 30% of U.S. voters cast their ballots by mail, according to federal data. In Michigan, where competitive U.S. House and Senate races could help determine the balance of power in Congress, the state said it has sent out more than 2 million absentee ballots for the state’s Aug. 4 primary.