A secret, highly contentious Republican memo reveals that Deputy Attorney General Rod J. Rosenstein approved an application to extend surveillance of a former Trump campaign associate shortly after taking office last spring, according to three people familiar with it.
The renewal shows that the Justice Department under President Trump saw reason to believe that the associate, Carter Page, was acting as a Russian agent. But the reference to Mr. Rosenstein’s actions in the memo — a much-disputed document that paints the investigation into Russian election meddling as tainted from the start — indicates that Republicans may be moving to seize on his role as they seek to undermine the inquiry.
The memo’s primary contention is that F.B.I. and Justice Department officials failed to adequately explain to an intelligence court judge in initially seeking a warrant for surveillance of Mr. Page that they were relying in part on research by an investigator, Christopher Steele, that had been financed by the Democratic National Committee and Hillary Clinton’s presidential campaign.
Democrats who have read the document say Republicans have cherry-picked facts to create a misleading and dangerous narrative. But in their efforts to discredit the inquiry, Republicans could potentially use Mr. Rosenstein’s decision to approve the renewal to suggest that he failed to properly vet a highly sensitive application for a warrant to spy on Mr. Page, who served as a Trump foreign policy adviser until September 2016.
A handful of senior Justice Department officials can approve an application to the secret surveillance court, but in practice that responsibility often falls to the deputy attorney general. No information has publicly emerged that the Justice Department or the F.B.I. did anything improper while seeking the surveillance warrant involving Mr. Page.
Mr. Trump has long been mistrustful of Mr. Rosenstein, the Justice Department’s No. 2 official, who appointed the special counsel, Robert S. Mueller III, and now oversees his investigation into Mr. Trump’s campaign and possible obstruction of justice by the president. Mr. Trump considered firing Mr. Rosenstein last summer. Instead, he ordered Mr. Mueller to be fired, then backed down after the White House counsel refused to carry out the order, The New York Times reported last week.
Mr. Trump is now again telling associates that he is frustrated with Mr. Rosenstein, according to one official familiar with the conversations.
It is difficult to judge whether Republicans’ criticism of the surveillance has merit. Although House members have been allowed to view the Republican memo in a secure setting, both that memo and a Democratic one in rebuttal remain shrouded in secrecy. And the applications to obtain and renew the warrant from the Foreign Intelligence Surveillance Court are even more closely held. Only a small handful of members of Congress and staff members have reviewed them.