He said that Project Veritas attempted to return the diary to the Justice Department and a lawyer representing Ms. Biden, who he said refused to take it. Mr. O’Keefe portrayed the investigation as politically motivated, questioning why the Justice Department under Ms. Biden’s father was pursuing the case.
In recent weeks, federal investigators have reached out to at least one person who worked for Project Veritas to question that person about the diary, one of the people briefed on the case said.
Project Veritas has a history of targeting Democratic congressional campaigns, labor organizations, news media and others. The group conducts sting operations, using hidden cameras and fake identities. At one point, Project Veritas relied on a former British spy named Richard Seddon to help train its operatives, teaching them espionage tactics such as using deception to secure information from potential targets.
Flyover Media, the company that owns the website that published the pages from the diary, is registered to the same Sheridan, Wyo., address as Mr. Seddon’s company, Branch Six Consulting International. Mr. O’Keefe, the founder of Project Veritas, was once the president of a company that later registered at the same address.
Project Veritas has a pending libel suit against The New York Times over a 2020 story about a video the group made alleging voter fraud in Minnesota.
Ms. Biden, 40, is Mr. Biden’s youngest child. She has maintained a low profile and attracted far less attention than Hunter Biden, her half brother. In 2019, Mr. Trump withheld military aid from Ukraine at the same time he pressured that country’s president for support in investigating Hunter Biden’s business dealings, leading to Mr. Trump’s first impeachment.