As Donald Trump finds his tenure in the White House connected with yet more allegations, the inevitable “i” word begins to pop up.
It was discussed by his opponents as a possibility even before his inauguration, but has yet to be tabled by anyone.
This is despite a string of controversies. Just this week, US media reported allegations he had asked FBI chief James Comey to drop an inquiry into links between his ex-national security adviser and Russia, while 24 hours before it was claimed he had let slip details of top secret intelligence to the Russian ambassador.
But how easy is it to impeach a president? And exactly who has been impeached in the past? The answer may surprise you….
Just what is impeachment?
The aim for those bringing charges when someone is impeached is the accused’s eventual removal from office – whether they be president of the US, or an official.
The US constitution states a president “shall be removed from office on impeachment for, and conviction of, treason, bribery, or other high crimes or misdemeanours”.
Exactly what “high crimes and misdemeanours” covers is up for debate.
The process of impeachment has to be started by the House of Representatives, and only needs a simple majority to pass. A trial will be set in the Senate.
But here, a two-thirds vote is necessary for removal – and this milestone has never been reached in America’s history.
Who has actually been impeached?
Despite it being threatened on numerous occasions, only two presidents have ever actually been impeached.
Most recently, Bill Clinton – the 42nd president of the United States – found himself impeached on the grounds of perjury in front of a grand jury and obstruction of justice, after he lied about the nature of his affair with Monica Lewinsky and then allegedly asked her to lie about it as well.
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The House voted 228 to 206 in favour of impeaching President Clinton for the first charge, and 221 to 212 on the second.
It should be noted that, at the time in December 1998, Mr Clinton’s approval rating as president was at 72%.
However, when it reached the Senate in 1999, it failed to get close to the two-thirds backing it needed in order to pass. As an analysis piece the BBC ran at the time noted, “in their eagerness to bring down the president, they never stopped to think whether the charges could be proved beyond reasonable doubt”.
The second? Clue: It wasn’t Richard Nixon. (More on this lower down).
In fact, the only other president impeached was Andrew Johnson, who served for four years from 1865 – the 17th person to hold the role.
He was impeached by the House in 1868. The vote came just 11 days after he got rid of Edwin Stanton, his secretary of war – a man who didn’t agree with his policies.
The parallels between Mr Stanton’s firing and that of Mr Comey – a man who also reportedly disagreed with Mr Trump – have not gone unnoticed in the American press.
Unlike Mr Clinton, however, Mr Johnson’s survival was a close call: the two-thirds majority was missed by just one vote, thanks to a number of Republicans.
Later, Iowa senator James Grimes explained: “I cannot agree to destroy the harmonious working of the Constitution for the sake of getting rid of an unacceptable president.”
So – could Mr Trump be impeached?
In theory yes. He could technically be accused of violations of his oath of office to “preserve, protect, and defend” the US constitution, according to the writers of Lawfare Blog.
In practice, however, it is far more unlikely.
As the BBC’s North America reporter Anthony Zurcher points out, “if this were a Democratic-controlled House of Representatives, articles of impeachment would likely be in the drafting process”.
The fact is, they are not. The Republicans control the House by 238 to 193. They control the Senate by 52 to 46, plus two independents.
The vast majority of Republicans have remained loyal to President Trump despite his approval ratings dropping to ever increasing lows. Monitoring website FiveThirtyEight puts the average at just 39.9% – and that is based on polls taken before this week.
Read Anthony Zurcher’s full blog: How damaging is this for Trump?
Of course, there are the notable exceptions. Senator John McCain told a dinner this week that the scandals surrounding the President are reaching “Watergate size and scale”.
Others are playing down each and every bump in the road. But there are beginning to be signs of exasperation within the party.
“Can we have a crisis-free day?” Republican Senator Susan Collins of Maine reportedly told CNN. “That’s all I’m asking.”
Even Senate majority leader, Senator Mitch McConnell, said the White House could do with “a little less drama”.
But thoughts will soon be turning to the forthcoming elections in 2018, and every candidate will surely have to ask: is this president hurting my chances?
Finally: just how did Mr Nixon avoid impeachment?
He did what every sensible person does when they know the tide has turned against them. He quit.