Can Donald Trump be impeached over the Russia and Comey scandals?
Allegations that Donald Trump asked FBI Director James Comey to end an investigation into Michael Flynn's links to Russia have spurred calls for the president to be impeached.
The explosive new development, stemming from a memo written by Mr Comey, followed a week of tumult at the White House after Mr Trump fired the FBI director and then discussed sensitive national security information about Islamic State with Russian Foreign Minister Sergei Lavrov.
Even before the latest bombshell had hit the White House, at least two congressional Democrats had demanded the president be impeached, but Democratic House leader Nancy Pelosi had pushed back against those isolated calls.
However, the clamour grew in the wake of the latest claims. David Axelrod, Barack Obama's former senior advisor, tweeted: "I've been resistant to impeachment talk until now, but if Comey memo is true-and Comey is very credible-we are into a whole new deal here."
Here's a look at what needs to happen for Mr Trump to be impeached.
What is impeachment?
Impeachment is the process by which Congress puts certain officials, namely the president, on trial. The constitution lays out a broad scope of offences that can lead to impeachment: “Treason, bribery, or other high crimes and misdemeanors”.
It does not mean the president will necessarily be kicked out of office. It proceeds like a bill passing through legislature. First, a majority in the House of Representatives - 218 out of 435 members - must approve articles of impeachment previously approved in committee.
Consequently, the current make-up of the House favours Mr Trump. As it stands, Republicans hold 238 seats while Democrats hold 193. (Four seats are vacant.) That means 25 Republicans would need to be persuaded to vote to impeach Mr Trump, which seems an unlikely scenario.
Then it goes to the Senate, where a two-thirds majority vote is needed to convict the president and consequently remove him from office - even getting the 60 votes needed to overcome a filibuster is difficult for either party these days.
What does history tell us?
History books show impeachment is far from straightfoward. There have been two presidents who have been impeached in the past and neither were removed from office.
Andrew Johnson was the first leader to go through the process in 1868. He was charged with breaking the law after he tried to replace the US secretary of war, Edwin Stanton, without congressional permission. At the time - in the aftermath of the civil war - the president was required to consult the senate about such decisions. His impeachment passed to the Senate, where he escaped being removed from office by a one-vote margin.
The other president was, of course, Bill Clinton over the Monica Lewinsky scandal. He was impeached for perjury and obstruction of justice in 1998, but he was acquitted in the Senate trial.
Richard Nixon would almost certainly have faced impeachments proceedings in 1974 over the Watergate scandal and undoubtedly would have been removed from office. However, the disgraced president resigned before it got that far and he handed the presidency over to Gerald Ford.
What could Trump be charged with?
Many people have said Mr Trump is not fit to be president, but this is not an impeachable offence, even under the broad terms of the constitution. So what could he be charged with?
- Read More: Donald Trump defends 'absolute right' to share information with Russia, amid row over classified intelligence
- Read More: President 'asked former FBI director Comey to shut down Flynn probe'
There were calls for action against him over the allegations that he shared classified information with the Russians. But if true, it is unlikely he has broken any law. As president, he has broad authority to declassify government secrets, which is why he defiantly defended himself by saying he had the "absolute right" to do so.
Other have pointed to his conflict of interest over his business dealings. Legal scholars have pointed out that as soon as he was sworn into office, he was in direct violation of the foreign-emoluments clause in Article I, Section 9, of the Constitution, which states: "... no person holding any Office of Profit or Trust under [the United States], shall, without the Consent of the Congress, accept of any present, Emolument, Office or Title of any kind whatever, from any King, Prince or foreign State.” With significant financial interests all over the world, this indeed a murky area for Mr Trump but he has taken enough steps away from his business empire to ensure this is a non-starter.
The latest controversy could be trickier for Mr Trump. Obstruction of the justice was one of the charges against Mr Clinton and the same charges were being levelled against the president as soon as he fired Mr Comey, who was leading an investigation into the Trump campaign's links to Russia. Mr Comey's memo claiming that Mr Trump urged him to end the investigation into Mr Flynn has only fuelled those accusations.
"The memo is powerful evidence of obstruction of justice and certainly merits immediate and prompt investigation by an independent special prosecutor," said Democratic US Senator Richard Blumenthal.
So did he break the law?
Legal experts say Mr Trump is certainly on thin ice over his comments, as quoted in the memo.
"For the president to tell the FBI to end a potential criminal investigation, that's obstruction of justice," said Erwin Chereminsky, a constitutional law professor and dean of University of California, Irvine School of Law. "This is what caused President Nixon to resign from office."
But the experts said intent was a critical element of an obstruction of justice charge, and the president's words could be subject to interpretation and possibly put into the context of other actions, like Mr Comey's termination.
The fact that the president apparently said he "hoped" Mr Comey would end the Flynn investigation rather than more directly ordering it "makes for a weaker but still viable case," Christopher Slobogin, a criminal law professor at Vanderbilt University Law School, told Reuters.
Mr Flynn's resignation came hours after it was reported that the Justice Department had warned the White House weeks earlier that Flynn could be vulnerable to blackmail for contacts with Russia's ambassador, Sergei Kislyak, before Mr Trump took office on January 20.
What next politically?
The case against Mr Trump would have to be damning and watertight for Republicans to act against him.
Republican US Representative Jason Chaffetz, chairman of a House of Representatives oversight committee, said his committee "is going to get the Comey memo, if it exists. I need to see it sooner rather than later. I have my subpoena pen ready".
The White House remained defiant as it denied the report.
"While the President has repeatedly expressed his view that General Flynn is a decent man who served and protected our country, the President has never asked Mr Comey or anyone else to end any investigation, including any investigation involving General Flynn," the White House said in a statement.
Not only are Republicans and Democrats demanding to see the memo, they also want Mr Comey to testify.
Republican Senator Lindsey Graham said: "Let's get to the bottom of what happened with the director. And the best way to get to the bottom of it, is for him to testify. ... I'm not going to take a memo, I want the guy to come in. If he felt confident enough to write it down, he should come in and tell us about it."
Democratic Senator Dianne Feinstein said Mr Comey needed to come to Capitol Hill and testify, while Senator Mark Warner, the top Democrat on the Senate Intelligence Committee, said he would ask Mr Comey for additional material as part of the panel's investigation. "Memos, transcripts, tapes - the list keeps getting longer," he said.