Attorney General William P. Barr has indicated that he is troubled by the possibility that the FBI conducted surveillance on the 2016 presidential campaign of Donald Trump. The president has regularly tweeted that he was a victim of spying. Trump’s allies in Congress have reiterated that claim.

There are two main threads to the accusations of spying: contacts by FBI-linked operatives with George Papadopoulos, a young Trump foreign policy aide, and federal court surveillance of Carter Page after he was ousted by the campaign. For instance, Rep. Jim Jordan (R-Ohio) tweeted:

“Now we know they spied on at least two American citizens associated with the Trump campaign 1) Carter Page — using the false Dossier as the basis for a secret warrant 2) George Papadopolous — set up by an FBI agent posing as a Cambridge professor’s assistant.”

Barr told the Senate on Wednesday that he intended to look into the matter, though he described what is known so far as “a fairly anemic” attempt: “Many people seem to assume that the only intelligence collection that occurred was a single confidential informant and a FISA warrant. I would like to find out whether that is, in fact, true. It strikes me as a fairly anemic effort if that was the counterintelligence effort designed to stop the threat as it’s being represented.”

As a service for readers who may be confused about the claims and counterclaims, here’s what we know, based on special counsel Robert S. Mueller III’s report, legal filings, Papadopoulos’s memoir, “Deep State Target,” Greg Miller’s “The Apprentice,” and news reports. Michael Horowitz, the Justice Department inspector general, is examining the FBI’s handling of the probe, so we may learn more eventually.

It’s clear the Justice Department was investigating possible ties between Russia and Trump campaign officials. The question is whether the investigation ever crossed a line into spying on the campaign itself — and that so far has not been proved.

The Fact Checker will update this article with additional details as they become available.

The Players

George Papadopoulos: A then-28-year-old foreign policy aide to the Trump campaign from March 2016 through early October 2016, when he was dismissed after an interview he gave to a Russian news agency generated negative publicity. He pleaded guilty to lying to the FBI but now says he was the victim of a “deep state” plot.

Carter Page: Another foreign policy aide, who served from March 2016 until the end of September, when he announced he had resigned because of continuing questions about his Russia contacts.

Joseph Mifsud: A Maltese professor who the Mueller report says is linked to Russian intelligence. He tried to broker meetings between Papadopoulos and Russians. On April 26, 2016, he met with Papadopoulos after a visit to Moscow and told him that the Russians had obtained “dirt” on Hillary Clinton in the form of “emails of Clinton” and that they “have thousands of emails.” The conversation took place after the Main Intelligence Directorate of the General Staff of the Russian Army, known as the GRU, had obtained access to Democratic National Committee emails and the email account of John Podesta, Clinton’s campaign chairman, according to the Mueller report.

Stefan Halper: University of Cambridge professor and confidential source for the FBI who reached out to three Trump foreign policy advisers, including Papadopoulos, during the 2016 election.

“Azra Turk”: Woman identified to Papadopoulos as Halper’s assistant, now said to be a government investigator, according to the New York Times, though the agency is not identified.

The Investigation

Crossfire Hurricane was the name of the FBI’s counterintelligence investigation, which was opened in late July 2016 after the Australian government reported that Papadopoulos told Alexander Downer, the top Australian diplomat to the United Kingdom at the time, during a May meeting that the Russian government had “damaging” material on Clinton and was prepared to release it late in the election. That conversation allegedly took place 10 days after Papadopoulos learned of the emails from Mifsud on April 26.

Papadopoulos claims to have no memory of the conversation with Downer and has accused the diplomat of being part of a plot to spy on him. In his memoir and to investigators, however, he admitted telling Nikolaos Kotzias, the Greek foreign minister: “I’ve heard the Russians have Hillary Clinton’s emails.” He says Kotzias immediately responded: “Do not ever repeat that again. That is not something that should ever be mentioned.”

The FBI and Papadopoulos

After then-candidate Trump visited The Washington Post editorial board on March 21, 2016, and named five members of his foreign policy team, including Papadopoulos and Page, foreign governments and intelligence agencies scrambled to learn more about individuals who appeared to have the ear of the unconventional candidate. “George Papadopoulos, he’s an energy and oil consultant, excellent guy,” Trump said.

The special counsel said campaign officials reported not being told by Papadopoulos about Mifsud’s revelation, even though Papadopoulos apparently communicated the information about Russian “dirt” to two foreign diplomats and was in regular communications with campaign officials. “The campaign officials who interacted or corresponded with Papadopoulos have similarly stated, with varying degrees of certainty, that he did not tell them,” the report said.

Meanwhile, Downer had sent a cable back to the Australian capital about his meeting with Papadopoulos. He had sought the meeting to gain some insight into Trump’s foreign policy views but decided that Papadopoulos was “surprisingly young and inexperienced” to amount to anything in a Trump administration. Buried in the cable was a reference to Papadopoulos saying the Russians had damaging material on Clinton and were prepared to use it. (In Downer’s telling, Papadopoulos did not mention emails.) But the cable was considered a routine recounting of a diplomatic contact.

After WikiLeaks started releasing DNC emails during the Democratic National Convention, held July 25-28, Downer suddenly remembered “with a shudder” his meeting with Papadopoulos, according to Miller’s book. He immediately requested a meeting with the top U.S. diplomat in the United Kingdom at the time, who in turn alerted the FBI. The FBI opened a counterintelligence operation on July 31.

About a month after the FBI launched the investigation, on Sept. 2, Papadopoulos said he received an email “out of the blue” from Halper. “He claims to be leading a project on the Turkey-European Union relationship and how the gas fields in Israel and Cyprus play into that,” he wrote in his memoir. “He notes that I’m a recognized expert in this field and offers to pay me $3,000 and fly me to London for discussions.” He views the invite as “win, win, win” and flies to London on Sept. 15.

Once he arrives, he gets a message from Turk, who says they should meet for a drink. “Azra Turk is a vision right out of central casting for a spy flick,” he wrote. “She’s a sexy bottle blonde in her thirties, and she isn’t shy about showing her curves — as if anyone could miss them. She’s a fantasy’s fantasy. ‘If this is what academic researchers look like, I’ve been going to the wrong school,’ I laugh to myself.”

Almost immediately, he claims, she starts asking about Trump and Russia: Is the campaign working with Russia? In one of the meetings with Halper, he says, the same thing happens: A series of leading questions about Trump, Russia and hacked emails. Papadopoulos says he angrily ended the meeting. Halper seemed “quite disappointed,” he told congressional investigators. “I think he was expecting something else.”

The New York Times reported the FBI “decided to send Ms. Turk to take part in the operation” and “to pose as Mr. Halper’s assistant.” Papadopoulos provided the newspaper with messages from Turk to him. She wrote that meeting him had been the “highlight of my trip. … I am excited about what the future holds for us :).” (These messages are not described in his book.)

In the interview with congressional investigators, Papadopoulos said that Turk’s “English was very bad.” He said he assumed she was a Turkish national. (It’s possible she used a fake accent.)

Halper also made contact with Page and another Trump campaign official, Sam Clovis. But both men have described the conversations as not suspicious. He did not ask probing questions about Russia.

Thus far, it’s unclear whether the Halper-Turk contacts with Papadopoulos amounted to much. By Papadopoulos’s account, he did not provide them with any useful information. He then initially misled FBI agents about his conversations with Mifsud, allowing the professor to depict the conversations as innocuous in his own interview with the FBI, in the lobby of a Washington hotel, on Feb. 10, 2017. Mifsud disappeared from sight and was not interviewed again.

“The false information and omissions in Papadopoulos’s January 2017 interview undermined investigators’ ability to challenge Mifsud when he made these inaccurate statements,” the Mueller report says. (There is no indication that Mifsud faces charges for lying to the FBI.)

The FBI and Page

Other than the contact with Halper, which Page described as inconsequential, the FBI’s surveillance of Page came after he left the campaign in late September.

Page had traveled to Moscow July 7-8 and made a speech criticizing U.S. policy toward Russia that echoed Russian President Vladimir Putin’s views. He emailed the Trump campaign about his insights from the trip and met with Russian officials, including one from the Russian energy company Rosneft.

“Page said that, during his time in Moscow, he met with friends and associates he knew from when he lived in Russia, including Andrey Baranov, a former Gazprom employee who had become the head of investor relations at Rosneft, a Russian energy company,” the Mueller report said. “Page stated that he and Baranov talked about ‘immaterial non-public’ information. Page believed he and Baranov discussed Rosneft president Igor Sechin, and he thought Baranov might have mentioned the possibility of a sale of a stake in Rosneft in passing.”

Meanwhile, the FBI learned of reports being written by former British intelligence officer Christopher Steele, then working under contract with a research firm on behalf of the Clinton campaign and the DNC. Steele had been an FBI source, and the agency found him to be credible. One of his reports, dated July 19, alleged various meetings between Page and Russian officials, including that Page met with Igor Diveykin, Putin’s deputy chief for internal policy, for a discussion of “kompromat,” or damaging material, on Clinton that might be given to the Trump campaign.

Such a meeting was not confirmed by the Mueller report. It noted that “Page’s activities in Russia—as described in his emails with the campaign—were not fully explained.”

Page had already come to the attention of the FBI before he joined the Trump campaign because of his interactions with Russian intelligence officers. In 2015, three of the people whom Page interacted with were charged with conspiracy to act as an unregistered agent of a foreign government, with the interactions with Page forming a key part of the complaint. One of the men pleaded guilty and was sentenced to 30 months in prison; the other two no longer lived in the United States and have not been arrested.

On Sept. 26, 2016, Page announced he had resigned from the Trump campaign. About a month later, on Oct. 21, as part of the investigation into Russian interference in the election, the FBI made an initial application for a Foreign Intelligence Surveillance Act (FISA) warrant to monitor Page’s conversations. The FISA warrant was approved and then renewed three times for 90-day increments by several judges.

“The target of this application is Carter W. Page, a U.S. person, and an agent of a foreign power,” the application said. “The FBI believes Page has been the subject of targeted recruitment by the Russian government.” The application noted he was a former foreign policy adviser of a candidate for U.S. president and that the “FBI believes that the Russian government’s efforts are being coordinated with Page and perhaps other individuals associated with Candidate #1’s campaign.”

The most controversial aspect of the application — much of which was redacted when released by the Justice Department under pressure from Congress — is that it relied in part on Steele’s reporting. The application noted he had been found “to be reliable” but added that the FBI speculated that he had been hired by someone “likely looking for information that could be used to discredit Candidate #1’s campaign.” Despite that potential bias, the application said “the FBI believes Source #1’s reporting herein to be credible.”

But many elements of Steele’s reporting for the “dossier” have not been confirmed and have been called into question by the Mueller report.

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