Suspicions, Demands and Threats: Devin Nunes vs. the Justice Dept.

The House speaker, Paul D. Ryan, has repeatedly and publicly backed Mr. Nunes. When Mr. Rosenstein and Christopher A. Wray, the F.B.I. director, came to Capitol Hill in January in a last-ditch effort to stave off an earlier subpoena, Mr. Ryan insisted that they comply and that Mr. Nunes would act responsibly. And when, weeks later, the department took rare public steps to try to block the release of a much-disputed memo drawn up by Republican committee aides from those documents, Mr. Ryan argued that Americans ought to be able to see the memo.

He offered similar support this time.

“This request is wholly appropriate,” Mr. Ryan told reporters on Thursday. “It’s completely within the scope of the investigation” by Mr. Nunes.

But Mr. Nunes’s handling of his secretive memo, released in early February, has been a source of lasting ill will. The document accused top F.B.I. and Justice Department officials, including Mr. Rosenstein, of abusing their authorities to spy on a former Trump campaign adviser suspected of being an agent of Russia. Law enforcement officials warned that the document was dangerously misleading and pointed out that Mr. Nunes had not read the underlying surveillance applications on which his four-page document was based.

Yet Mr. Trump seized on its findings to declare that he had been vindicated. And now, department officials said they were fearful that Mr. Nunes and his allies were seeking a repeat performance. More troubling, the officials said, is that Mr. Nunes’s actions suggest that he is more interested in courting conflict than understanding the case.

In the middle of another records dispute last month, Mr. Nunes threatened to hold Mr. Rosenstein in contempt or even try to impeach him if the Justice Department did not grant access to a nearly complete copy of a document used to open the Russia investigation in the summer of 2016, as well as material related to the wiretap of the Trump campaign aide, Carter Page. Mr. Rosenstein acquiesced and handed over the documents, but despite Mr. Nunes’s repeated demands, he never read them, according to an official familiar with the matter.

That did not keep Mr. Nunes from going on television to savage those very decisions.

In another meeting, Mr. Rosenstein felt he was outright misled by Mr. Nunes’s staff. Mr. Rosenstein wanted to know whether Kashyap Patel, an investigator working for Mr. Nunes who was the primary author of the disputed memo, had traveled to London the previous summer to interview a former British spy who had compiled a salacious dossier about Mr. Trump, according to a former federal law enforcement official familiar with the interaction.

Mr. Patel was not forthcoming during the contentious meeting, the official said, and the conversation helped solidify Mr. Rosenstein’s belief that Mr. Nunes and other allies in Congress were not operating in good faith.