“It’s embarrassing. It’s sloppy. I’ve run out of words,” Mr. Comey said.
But he insisted that the wiretap of Mr. Page, a relatively junior aide who had left the campaign before the F.B.I. secured a court order to wiretap him based on suspicions about his ties to Russia, was a “slice” of the larger effort to determine whether Mr. Trump and his team were conspiring with Russia’s election interference operations. And he angered Republicans by repeatedly saying he could not remember details of the case.
“With all due respect, Mr. Comey, you don’t seem to know anything about an investigation that you ran,” said an irate Senator Mike Lee, Republican of Utah.
The hearing was the committee’s third in recent months to scrutinize the investigation, and Mr. Graham intends to call Mr. Comey’s former deputy, Andrew G. McCabe, to testify next week.
Mr. Graham, who is locked in his own unexpectedly tight re-election fight, insisted that he would keep going until “one of the most corrupt investigations in modern history” was exposed and officials involved were either “fired or go to jail.” A former F.B.I. lawyer has pleaded guilty to falsifying a document used in preparations for the warrant application. He was prosecuted as part of another ongoing review of the investigation, led by John H. Durham, a federal prosecutor Mr. Barr appointed.
During the hearing, Mr. Graham released a letter from the Justice Department, stating that an unnamed low-level department lawyer who had signed the warrant application also now regretted it and claimed the F.B.I. had withheld key facts.
Republicans were most animated by the F.B.I.’s use in the warrant applications of a dossier of unverified information compiled by a British former spy, Christopher Steele. Mr. Steele’s work was funded, in part, by Democrats, and it drew from information provided by a Russian source who Republicans said could have been spreading misinformation. Agents relied on the dossier in part to secure court permission for the Page wiretaps, while sharing few details with the court about its provenance.
But if Republicans had hoped to use Mr. Comey to score political points, Democrats sought his help backing up their criticisms of Mr. Trump and Mr. Barr.