Markwayne Mullin, the homeland security secretary, has asked the Justice Department to examine whether a commonly used voting machine can be trusted to create a verifiable record, in what appeared to be the Trump administration’s latest effort to cast doubt on digital voting systems.

In a letter to Attorney General Todd Blanche on Wednesday, Mr. Mullin asked the Justice Department to determine whether devices that tally votes through bar codes or QR codes provided what he described as a “reliable record for a manual audit.”

The letter, which asked Mr. Blanche for his department’s help in ensuring that machines known as ballot-marking devices comply with federal law, raises questions about whether the request sought to lay the ground for claiming that some electronically cast or counted votes are invalid.

Unlike the process of voting by handwritten ballot, ballot-marking devices rely on ballots printed from a touch-screen computer. The ballots, which typically designate a voter’s choice in text form and in a bar code or QR code, are then fed into a separate machine that reads the information.

Critics of the devices have claimed that hackers could in theory manipulate the digital codes, though election integrity experts say there are no examples of that happening in an election. The devices have been widely used in states like Georgia and South Carolina, where Mr. Trump has won elections.

Election machines are already heavily monitored and regulated through testing and certification by federal agencies, states, local election offices and private labs. (The Trump administration recently forced out the independent members of the Election Assistance Commission, which oversees the certification of machines).

In his letter to Mr. Blanche, Mr. Mullin asked the Justice Department to investigate another pillar of the country’s election infrastructure: a multistate partnership called the Electronic Registration Information Center, or ERIC.

ERIC, a database-sharing consortium that helps states ensure that people vote in only one location, was once considered a wonky, bipartisan initiative to help states clean their voter rolls. But in recent years, it has become a target of election conspiracy theorists trying to sow doubt in the process of administering elections.

In his letter, Mr. Mullin indicated that the requests had initially been made to the Justice Department under his predecessor, Kristi Noem, who was ousted in March. The letter, which congratulated Mr. Blanche on being confirmed as attorney general last month, appeared to be an attempt to nudge him into action less than 60 days before the midterm elections.

President Trump has long complained about electronic voting systems, falsely claiming that they were used in a sprawling plot to rig the 2020 election against him. In March 2025, just two months after he returned to the White House, he issued an executive order in which he “raised the issue of the security of voting systems that rely on bar codes and QR codes,” Mr. Mullin noted in his letter.

Mr. Trump reprised his attacks against these machines in a prime-time address two months ago, saying they were “vulnerable” and “easily compromised.” The president pointed to a trove of declassified intelligence documents to make his case, especially those related to a technology company called Smartmatic, which he said had ties to the Venezuelan government.

But Mr. Trump’s claims about Smartmatic’s devices far outran the problems with them that were described in the declassified materials. One of the documents, a C.I.A. analysis, said that while the Venezuelan government had “some capability in manipulating electronic voting systems,” neither it nor Smartmatic could “manipulate the outcome of an election outside Venezuela.”

Mr. Mullin’s letter did not mention Smartmatic by name. But it did refer to an effort last winter by senior Trump intelligence officials to examine the vulnerabilities of machines built by another company, Dominion Voting Systems, now known as Liberty Vote, which has also been at the center of outlandish conspiracy theories.

Conspiracy theories have also long underpinned the conservative efforts to dismantle ERIC. In the aftermath of the 2020 election, election deniers successfully pressured secretaries of state in many Republican states to withdraw from ERIC, claiming it was a front for left-wing groups to organize voter-registration drives.

Those claims were largely promoted by Heather Honey, then a researcher and activist who is now a top official at the Department of Homeland Security working with Cleta Mitchell, a conservative lawyer who played a role in Mr. Trump’s attempts to overturn the 2020 election. Ms. Honey presented a report to several Republican secretaries of state in the summer of 2022 claiming ERIC was inappropriately influenced by partisan Democrats and left-wing groups.

As a result, nine Republican-led states withdrew from ERIC. But nearly 30 states now still use the system.

ERIC is currently the only system that can reliably catch whether people vote in more than one state. And election officials widely agree that it also helps to identify dead people on voting lists.

Mr. Mullin’s letter suggested that data from ERIC, including “protected motor vehicle data,” had been with an organization called the Center for Election Innovation and Research, a nonpartisan group that works to build confidence in elections. Mr. Mullin told Mr. Blanche that sharing such information with a nongovernmental organization could violate federal privacy laws.

The Center for Election Innovation and Research is run by David Becker, a former voting rights lawyer for the Justice Department who also helped to found the ERIC system. Mr. Becker has vehemently criticized the Trump administration’s attempts to interfere with elections, raising questions about whether the request to investigate ERIC was also an effort to target him and his group.

Mr. Becker said in a statement on Friday that the allegation from Mr. Mullin likely related to research his organization performed over five years ago. Mr. Becker also rejected claims made by Mr. Mullin that the organization received motor vehicle or voter data on an ongoing basis.

“There have been multiple public documents published as far back as early 2022 relating to this research,” the statement said, adding that no one from the Department of Homeland Security contacted the center for “information or clarification” before Mr. Mullin issued his letter.