WASHINGTON — The former deputy attorney general Rod J. Rosenstein will testify before senators next week in a hearing that will give President Trump’s allies a high-profile platform to escalate their attacks on the Russia investigation.
Mr. Rosenstein was a key figure in the inquiry. In May 2017, he appointed Robert S. Mueller III to serve as special counsel overseeing the investigation into possible links between Russia’s 2016 election interference and Trump associates. Mr. Trump has long attacked the investigation and other efforts by national security officials to understand Moscow’s election subversion operations as instead a plot to undercut him.
Senator Lindsey Graham, Republican of South Carolina and the chairman of the Judiciary Committee, invited Mr. Rosenstein to appear before the panel and said in a statement that he would be the first of several witnesses to testify about the investigation. Mr. Rosenstein left the Justice Department in May 2019 and was hired this year by the law firm King & Spalding.
Mr. Trump has publicly pressured Mr. Graham to hold hearings on the Russia investigation and interrogate his perceived enemies. The president has long attacked many of the inquiry’s key figures — including Mr. Mueller, the former F.B.I. director James B. Comey and Mr. Comey’s deputy, Andrew G. McCabe — and he has recently ramped up unsubstantiated accusations that former President Barack Obama masterminded a scheme against him.
Mr. Graham is among the Trump allies who have sought to conflate the broader Russia investigation with narrower aspects of it that an independent watchdog has faulted. Mr. Graham said that Mr. Rosenstein would address findings in a report by the Justice Department inspector general, Michael E. Horowitz, that investigators’ applications to wiretap a former Trump campaign adviser, Carter Page, were riddled with errors and other problems.
Mr. Rosenstein signed off on one of the renewal applications. But in a statement, he seemed to be distancing himself from others involved in the Russia investigation. He said that he had learned that “even the best law enforcement officers make mistakes, and that some engage in willful misconduct.”
“Independent law enforcement investigations, judicial review and congressional oversight are important checks on the discretion of agents and prosecutors,” Mr. Rosenstein said. “We can only hope to maintain public confidence if we correct mistakes, hold wrongdoers accountable and adopt policies to prevent problems from recurring.”
Mr. Mueller’s investigators ultimately found insufficient evidence to charge anyone in Mr. Trump’s orbit with conspiring with Russia’s election interference. They detailed the president’s attempts to impede their inquiry and ultimately chose not to charge him, citing legal and factual constraints, but pointedly declined to exonerate him.
Attorney General William P. Barr has also chipped away at the results of the investigation. Weeks after being sworn in last year, Mr. Barr said that he would scrutinize its origins, and he has made clear that he believes it was opened without legitimate rationale. He also raised the possibility that members of the Trump campaign were inappropriately spied on, and this month he moved to withdraw the Justice Department’s case against the former national security adviser Michael T. Flynn, who had pleaded guilty to lying to investigators in the Russia inquiry.
After the Mueller report was released, Mr. Barr asked the top federal prosecutor in Connecticut, John H. Durham, to investigate the department’s decision to open the inquiry, known internally as Crossfire Hurricane.
The Russia investigation dominated the public perception of Mr. Rosenstein’s tenure. The president has said that he fired Mr. Comey upon a recommendation from Mr. Rosenstein, who had ascended to the No. 2 job in the Justice Department days earlier and written a memo supporting the dismissal.
As law enforcement officials debated in the chaotic ensuing days over whether to investigate Mr. Comey’s dismissal as obstruction of justice, Mr. Rosenstein suggested that he wear a wire to secretly record Mr. Trump in the White House, according to memos by Mr. McCabe and other F.B.I. officials. Mr. Rosenstein also discussed recruiting cabinet members to invoke the 25th Amendment to remove the president from office for being unfit. Mr. Rosenstein has denied those accounts.
Mr. Rosenstein decided to install Mr. Mueller to take over the inquiry days after the president fired Mr. Comey, and Mr. Graham told Fox News that he intended to ask Mr. Rosenstein about his legal rationale for the appointment.
Mr. Rosenstein later complained to others at the Justice Department that he had been manipulated and used by the White House to provide cover for the dismissal of Mr. Comey, which Democrats and some Republicans condemned.