A REVEALING TIME FOR DONALD TO START PAYING OFF HIS DEBTS:

The most prominent of the C.I.A.'s sources of intelligence on Russia's election interference was a person close to Mr. Putin who provided information about his involvement, former officials have said. The source turned over evidence for one of the last major intelligence conclusions that President Barack Obama made public before leaving office: that Mr. Putin himself was behind the Russia hack.

Long nurtured by the C.I.A., the source rose to a position that enabled the informant to provide key information in 2016 about the Russian leadership's role in the interference campaign, the officials said.

John O. Brennan, the C.I.A. director under Mr. Obama, would bring reports from the source directly to the White House, keeping them out of the president's daily intelligence briefing for fear that the briefing document was too widely disseminated, according to the officials. Instead, he would place them in an envelope for Mr. Obama and a tiny circle of aides to read.

But Mr. Trump's promise to declassify a broad swath of documents suggests that Mr. Barr's mandate is more extensive than investigating any single source. Mr. Trump's comments mentioning Britain and Australia appeared to be a reference to the F.B.I.'s investigation of George Papadopoulos, a former Trump campaign aide.

An Australian diplomat told the F.B.I. in the summer of 2016 that Mr. Papadopoulos had said that Russia had made an offer to help the Trump campaign by releasing stolen Democratic emails. The F.B.I. enlisted an informant, Stefan Halper, to talk with Mr. Papadopoulos, an investigative technique that prompted Mr. Trump to accuse the bureau of spying on his campaign.

Mr. Barr has picked up on the term "spying," invoking it multiple times in recent weeks to describe steps the F.B.I. took to investigate the Trump campaign but stopping short of alleging that the bureau acted improperly.

It would have been improper for the intelligence agencies to sit on the information from Mr. Papadopoulos, Mr. King said.

"If someone came and told that to the C.I.A. or F.B.I. and they didn't open a counterintelligence investigation, they would be guilty of malpractice," he said. "If they had ignored that, it would have been unacceptable law enforcement, especially when we are dealing with an adversary trying to undermine our country."

He also said the Intelligence Committee looked at both the F.B.I.'s and the C.I.A.'s role in the origins of the Russia inquiry. He said the C.I.A. and the National Security Agency played roles in the inquiry, but said that was proper.

Some revelations about intelligence operations around the 2016 campaign have angered officials in Britain, Australia and other closely allied countries, according to former officials. Exposing further information about British or Australian cooperation in the investigation could deepen tensions with two of America's closest intelligence partners.

"It is yet another step that will raise questions among our allies and partners about whether to share sensitive intelligence with us," said Michael Morell, the former deputy director of the C.I.A. and host of the "Intelligence Matters" podcast.

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