President Donald Trump's firing of FBI Director James Comey on 9 May renewed attention to allegations by US intelligence agencies that Russia interfered in the 2016 election campaign to benefit Trump.
The following describes what is publicly known and not known about US investigations into meddling and possible collusion between Russia and members of the Trump campaign:
How did the investigations begin?
Former President Barack Obama ordered US intelligence agencies to assess whether Russia tried to intervene in the election after a cyber attack on the Democratic National Committee in July 2016 and the publication of thousands of hacked personal emails from Hillary Clinton's campaign manager in the month before the 8 November election. Obama told intelligence officials to deliver a report on possible foreign interference before he left the White House in January 2017.
What did the intelligence agencies find?
The Central Intelligence Agency, the Federal Bureau of Investigation and the National Security Agency concluded in a report declassified in January that Russian President Vladimir Putin ordered a campaign not just to undermine confidence in the US electoral system but to affect the outcome.
The agencies said Putin and the Russian government had a “clear preference” for Trump to win the White House. Putin's associates hacked information, paid social media “trolls” and backed efforts by Russian government agencies and state-funded media to sway public opinion, the agencies said.
The report stopped short of assessing whether Russia succeeded in swaying the election result.
Putin and other Russian officials have repeatedly denied interfering in the US election. What has Trump said about Russia's role in the election?
Trump has not taken a clear public position.
“I will tell you this, Russia: if you're listening, I hope you're able to find the 30,000 emails that are missing,” Trump said at a July 2016 news conference, in reference to an FBI probe into Clinton's use of a private email system when she was secretary of state and emails that had possibly been deleted.
Trump subsequently dismissed reports, including from US intelligence officials, that Russia had attempted to intervene in the election on his behalf.
The first time Trump said he accepted the findings of the intelligence agencies was at an 11 January news conference ahead of his inauguration. “As far as hacking, I think it was Russia,” Trump said, although he added: “It could have been others also.”
Earlier this month, Trump said China may have hacked the emails of Democratic officials to meddle with the election, offering no evidence and countering the view of intelligence officials.
How many US probes are there into Russia's election meddling?
The Justice Department announced on 17 May that it has appointed Robert Mueller, a former FBI director, as special counsel to lead an independent Russia probe. Mueller would, if the evidence merits, work in tandem with the FBI, which is investigating, to handle any related criminal prosecutions.
Committees in the House of Representatives and the Senate are also investigating and those probes will continue. Comey has been invited to testify about the agency's Russia investigation and his dismissal. Has there been any fallout for Trump associates over contacts with Russia before, during or after the election campaign?
Michael Flynn, Trump's national security adviser, was fired in February. The White House said he had misled Vice President Mike Pence about the contacts he had with Russia's ambassador to the United States, Sergei Kislyak, before Trump took office.
On 9 May, federal prosecutors issued grand jury subpoenas seeking business records from people who worked with Flynn when he was a private citizen.
On 10 May, the Senate Intelligence Committee issued the first subpoena in its Russia investigation, demanding documents from Flynn after he declined to voluntarily comply with an earlier request.
Attorney General Jeff Sessions had to recuse himself from involvement in Russia-related probes at the Justice Department because he had not told Congress of his own contacts with Kislyak in 2016. Rod Rosenstein, the deputy US attorney general, is handling matters related to Russia; he appointed Mueller as special counsel. Will the FBI probe continue after Comey's dismissal?
Comey told the House Intelligence Committee on 20 March that the FBI was investigating Moscow's role in the election, including possible collusion with Trump's campaign. It was the first time he publicly acknowledged the agency was investigating the matter.
Comey's departure does not necessarily mean the FBI's Russia investigation will be disrupted or ended as the career FBI officials Comey put in charge of it will likely continue working on the matter even as the search for a new director begins.
FBI acting Director Andrew McCabe, who will lead the agency until a new director is named, promised the Senate Intelligence Committee that Comey's firing will not affect the investigation and that he will notify the committee of any attempt to delay or derail it.
Why was Comey fired?
Attorney General Sessions sent Trump a 9 May letter attaching a memo from Rosenstein, the deputy attorney general, on “Restoring Confidence in the FBI” that recommended Comey's dismissal.
Rosenstein's memo said Comey erred in July 2016 by announcing the FBI had been examining Clinton's use of a private email server and that the case should be closed without prosecution. Rosenstein's view was that Comey's decision to make a public statement on the matter broke with longstanding FBI precedent and should have been handled by the then-US attorney general, Loretta Lynch.
Trump called Comey a “showboat” and “grandstander” in an interview with NBC News on May 11, saying that he would have fired Comey regardless of Rosenstein's recommendation.
Did Comey's firing have anything to do with the Russia probe?
The White House says Comey was dismissed because of his handling of the Clinton email investigation.
The New York Times was the first to report, on 16 May, that a memo Comey wrote after a February meeting with Trump stated that the president had asked him to end the FBI's investigation of Flynn.
Trump aides have told Reuters that top Justice Department officials wanted a heads-up from Comey about what he would say during a 3 May congressional hearing about the FBI's investigation of Clinton's private email system.
The hearing was just days after Clinton said at a New York event that announcements by Comey in the week before the November election that he had re-opened, and then re-closed, the email probe had swung the election for Trump. Comey told the congressional panel the idea that he may have affected the election result made him “mildly nauseous.”
Is Trump being investigated by the FBI?
In the short letter Trump sent to Comey dismissing him from the FBI, he thanked Comey for informing him on three separate occasions that he was not under investigation. Comey has never stated publicly whether or not the FBI was investigating Trump and it would be unorthodox for him to say such a thing to the president. The White House has offered no proof to back Trump's claim.
News of Comey's memo, along with a Washington Post report on 15 May that Trump had revealed classified info during a 10 May meeting at the White House with Russian officials, intensified calls from Democrats and some Republicans for an independent probe of Trump's ties to Russia.
Trump has made clear on multiple occasions he believes the Russia investigations have run their course and should be closed. “The Russia-Trump collusion story is a total hoax, when will this taxpayer funded charade end?” he wrote on Twitter on 8 May.
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