President Donald Trump’s push to have the U.S. Postal Service screen voters for eligibility in the midterm election is running up against tight deadlines that some officials are warning will cause massive errors and disenfranchisement.

The Supreme Court this week temporarily allowed the Postal Service to move forward with a new plan — based on a Trump executive order — that would require states to submit lists of their eligible voters to the mailing agency, which would then ensure no ballots are mailed to individuals not on those lists.

While the rule faces several renewed legal challenges, USPS now has just weeks until some states begin sending out ballots ahead of the November elections, and it has to bring thousands of state and local offices up to speed on the new steps.

USPS has proposed something it has never done before, which would require a heavy lift, said Tom Day, a Postal Service executive for 35 years who spent parts of his career personally responsible for developing the network technology the agency would need to carry out its rule.

“This is not something where you just flip the switch and turn it on,” said Day, an appointed member of the Postal Regulatory Commission since 2023. “I don’t know how the hell they’re going to do it.”

Under Trump’s order, the agency must develop a process to cross-reference all outgoing ballots against still-to-be-submitted lists from states. While the Postal Service has for decades automated the processing of mail and reading of addresses, it has not used those capabilities to pick out mailers ineligible to use its network.

While states will maintain full control over who is on their eligibility lists, a final regulation put forward last week calls on USPS to do exactly that.

The Postal Service is currently working on technical solutions to implement the rule, according to a source familiar with the planning, who added that the agency is focusing on ensuring its review of mailed ballots against state-provided lists is error-free.

Day, however, said that was an impossible goal and erroneously denied ballots are inevitable.

“No system works at 100% accuracy,” he said.

The Postal Service typically would spend at least a year rolling out a new system like the one that will be required for ballot screening, hold a conference for all impacted jurisdictions and provide training to 8,000 election boards around the country, Day said.

He noted that without all of those steps, and with some states sending out ballots as soon as early September, he expects a 20% to 30% error rate, “and that would be a disaster.”

“We haven’t run the tests to give us the validity that the damn thing will work,” Day said. “To do it in three weeks, my God, there’s no way.”

Another senior postal official said the agency was placing significant burdens on states, an argument many states have made in federal court.

“We’re getting near Labor Day here,” the official said. “Just the uncertainty, I can only imagine trying to be a state election official. What can you do?”

The city of Madison, Wisconsin, and Travis County, Texas, in conjunction with outside groups, told a federal court on Tuesday that the Postal Service lacks sufficient staff to answer questions from jurisdictions around the country on the new process, alleging USPS employs just 40 specialized analysts to field those inquiries.

“Unanswered questions in this context risk disenfranchising voters,” they said in court filings.

They added that USPS must train tens of thousands of clerks, who previously have only received instruction on how to identify ballots and expedite their delivery, rather than on refusing to accept them.

In its final rule, the Postal Service said it would train its analysts and provide “additional resources as necessary” to ensure customers receive consistent and accurate advice.

The Postal Service said it will use a “straightforward” process to verify ballots are eligible for distribution, in part by requiring election officials to physically drop them off at designated points or post offices and stand and wait while they are checked. In their lawsuits, local officials suggested that plan was unworkable and would take an unrealistic amount of time.

The agency acknowledged, in response to comments on its proposed rule, that it was requiring states to adjust their processes and incur new costs, but said “any logistical or financial difficulties” and concerns that “immediate implementation would prove impossible” were outweighed by the law-enforcement benefits of the rule. The Postal Service declined to comment for this story.

States, local jurisdictions and advocacy groups are pursuing various legal pathways to stop USPS from implementing the rule. The Supreme Court has ruled only that rulings halting implementation of the executive order were premature before the Postal Service finalized its proposal, which it has now done. Challengers this week updated their lawsuits or filed new ones.

The Postal Service, in the final version of its ballot rule, maintained it has adequate staffing for enforcement and does not need to build new capacity, though it conceded that much of the work to implement the rule still lies ahead of it.

In addition to training staff, USPS still must develop guidance documents, the agency said in its regulatory filing, to make clear how to create an account to upload voter lists to its portal, assign users, properly format files and resolve errors.

USPS said it anticipated that states would continually update their lists, meaning its database of eligible voters will be evolving up until Election Day.

The uncertainty still remaining shows that the agency is creating a “unique process that USPS hasn’t done before,” the senior postal official said.

“If it was so easy, the Postal Service could point to, ‘Here’s how we already do it,’” the official said. “It raises questions.”

In a response to a separate challenge before the Postal Regulatory Commission, the Postal Service said the new rule was not entirely novel, likening it to regulations for mailing certain animals or electronic cigarettes, and that it was similar to standards it has for allowing cremated remains or replica explosives to enter the mailstream. It also told its regulator that voters would not see any direct disruption to their experience with the mail.

David Steiner, the U.S. postmaster general, previously told Congress that any state that does not submit its voter lists to his agency would be prohibited from using mailed ballots. States must also conform to new requirements for envelope and barcode design, though officials stressed that USPS has pushed for those standards for years and that many states already comply with them.

In the meantime, the Department of Homeland Security is, as required by Trump’s order, working with the Social Security Administration and State Department to provide data to states on eligible voters to help them compile their own lists.

NOTUS previously reported that DHS in June was still working on back-end development and initial testing for that data sharing. The databases it was tapping into were unreliable for the project of verifying voter eligibility, former federal officials said, and could also lead to large-scale errors.

Postal Officials Say Trump’s Mail-Ballot Push Will Create Widespread Errors