Former FBI Director James Comey will testify to the US Senate Intelligence Committee on Thursday about Russian involvement in the 2016 presidential election.
President Donald Trump's abrupt firing of Comey on May 9 renewed attention to allegations by US intelligence agencies that Russia interfered in the election to benefit Trump. It also raised questions about the motivations behind Comey's dismissal.
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 Nov. 8 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.
How many US probes are there into Russia's election meddling?
Comey told the House Intelligence Committee on March 20 that the FBI was investigating Moscow's role in the election, including possible collusion with Trump's campaign.
The Justice Department announced on May 17 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 to handle any related criminal prosecutions.
In addition there are multiple committees in the Senate and House of Representatives investigating various aspects of Russian election meddling.
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 a Jan. 11 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."
Trump said in May that China may have hacked the emails of Democratic officials to meddle with the election, offering no evidence and countering the view of intelligence officials.
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 May 8.
On May 30, Trump wrote on Twitter: "Russian officials must be laughing at the US & how a lame excuse for why the Dems lost the election has taken over the Fake News."
Did the FBI probe continue after Comey's dismissal?
There is no evidence that the FBI ended or paused its investigation after Comey's departure.
FBI acting Director Andrew McCabe, who is leading the agency, promised the Senate Intelligence Committee that Comey's firing would not affect the investigation and that he will notify the committee of any attempt to delay or derail it.
Trump on June 6 tapped former US Justice Department official Christopher Wray, who represented New Jersey Governor Chris Christie in the so-called Bridgegate scandal, to be the next FBI director. Wray will need Senate confirmation.
Why was Comey fired?
The White House cited a May 9 letter to Trump from Attorney General Sessions that attached a memo from Rod 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 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.
In an unorthodox move, Great America Alliance, an offshoot of a pro-Trump super PAC devoted to promoting the White House agenda, developed a television ad called "Showboat" to air as Comey testifies. The ad claims Comey was "consumed with election meddling" at the expense of fighting terrorism.
Was Comey's firing related to the FBI's Russia probe?
Whether Comey believes his firing was linked to the FBI's Russia probe will likely be a main focus when he testifies on Thursday.
Trump asked Comey to end the agency's investigation of Michael Flynn, his former national security adviser, and also to make some sort of public statement that he was not personally under investigation in order to clear "the cloud" hanging over his presidency, according to Comey's prepared testimony.
Comey found it "very concerning" that Trump would ask him to drop the agency's probe of Flynn and declined to state publicly that Trump himself was not under investigation, in part because it would create a "duty to correct" if that changed, according to the testimony.
"I need loyalty, I expect loyalty," Trump told Comey at a January 27 dinner, according to the testimony.
Less than a week before he was fired, Comey told a congressional panel that it made him "mildly nauseous" that he may have affected the outcome of the election by publicly re-opening, and then re-closing, the Clinton email probe days before the election.
Has there been any fallout for Trump associates over contacts with Russia before, during or after the election campaign?
Flynn 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 May 9, federal prosecutors issued grand jury subpoenas seeking business records from people who worked with Flynn when he was a private citizen. On May 10, the Senate Intelligence Committee issued the first subpoena in its Russia investigation, demanding documents from Flynn. He provided the first batch on June 6.
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. Rosenstein is handling matters related to Russia and it is he who appointed Mueller as special counsel.
Is Trump himself under investigation?
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 confirmed in his written testimony that he told Trump that he was not personally under investigation.