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 handwritten ballots, ballot-marking devices rely on ballots printed from a touch-screen computer, which are then fed into a separate machine that reads the information. Critics claim hackers could manipulate the digital codes, but election integrity experts say there are no examples of that happening.

In his letter, Mr. Mullin also asked the Justice Department to investigate the Electronic Registration Information Center, or ERIC, a multistate database-sharing consortium. Once a bipartisan initiative to help states clean voter rolls, ERIC has become a target of election conspiracy theorists. Mr. Mullin indicated the requests had initially been made under his predecessor, Kristi Noem, and appeared to nudge Mr. Blanche into action less than 60 days before the midterm elections.

President Trump has long complained about electronic voting systems, falsely claiming they were used to rig the 2020 election. He issued an executive order in March 2025 and reprised attacks in a prime-time address, pointing to declassified documents about Smartmatic. However, a C.I.A. analysis said neither the Venezuelan government nor Smartmatic could manipulate elections outside Venezuela.