The conviction of one key Donald Trump aide and the admission of guilt by another over a string of financial misdemeanours have once more raised the question of impeaching the US president.

Mr Trump’s long-serving attorney Michael Cohen and ex-campaign manager Paul Manafort were both found guilty by courts in New York and Virginia on Tuesday of charges arising from FBI special counsel Robert Mueller‘s ongoing investigation into the possibility of Russian agents conspiring to hack the 2016 presidential election.

Mr Cohen’s guilty plea included the confession that he had arranged to pay “hush money” to Playboy playmate Karen McDougal and porn star Stormy Daniels “at the direction of the candidate” to ensure they stayed silent on allegations he had sexual affairs with them prior to accepting the Republican nomination.

Here’s everything you need to know.

How does impeachment work?

In accordance with the US Constitution, impeachment can be instigated by a majority vote in the House of Representatives against any civil officer of the federal government, not just the president, if there is reason to suspect them of “treason, bribery or other high crimes and misdemeanours”.

The House Judiciary Committee investigates whether charges are warranted and, if the consensus is yes, articles are duly drafted laying out the accusations. These are then voted on by the House as a whole.

Assuming the vote passes in favour of impeachment, the articles are then handed on to the Senate, which serves as a court presided over by the chief justice of the United States, presently John Glover Roberts Jr. Senators swear an oath to do “impartial justice according to the Constitution and the laws”.

Managers are appointed from among the senators to prosecute the case, while the accused is entitled to present a defence during trial hearings. Once both sides have been heard, the Senate votes on each article of impeachment, conviction coming if two-thirds of members find the defendant guilty.

Should that happen, the Senate finally hands downs its punishment, be it removal from office or a ban on their ever holding federal authority again.

The vague nature of the phrase “high crimes and misdemeanours” has led to some disagreement about what precisely constitutes an impeachable offence. It is generally interpreted as meaning behaviour unbefitting of the office held or in violation of the public trust, rather than pushing an unpopular policy or acting incompetently.

As Gerald Ford once quipped: “An impeachable offence is whatever a majority of the House of Representatives considers it to be at a given moment in history.”

How likely is Donald Trump’s impeachment?

Brian Klaas, a former US campaign adviser, told The Independent Mr Trump had suffered both legal and political damage from Tuesday’s courtroom drama and there is now a “real risk” his former lawyer might cooperate with Mr Mueller’s probe and reveal further incriminating details of their time together.

“The odds of Trump either being impeached or somehow not finishing his term went up significantly yesterday,” Mr Klass said.

“There is a growing consensus among at least Democrats and independents, if not Mr Trump’s core base, that he is surrounding himself by criminals.

“There are a lot of people in Mr Trump’s inner circle who are either convicted of or pleading guilty to crimes.”

Cohen and Manafort became the third and fourth Trump allies to be charged as a result of Mr Mueller’s investigation, following ex-national security chief Michael Flynn and aide George Papadopoulos admitting lying to the FBI over the Trump camp’s associations with Russia.

Whether the alleged Stormy Daniels pay-off is enough to merit impeachment is open to doubt. Its impact on the election campaign was, after all, indirect, potentially affecting Mr Trump’s public image with voters but not the electoral process in itself.

Further revelations could yet appear, of course, as the president is not without enemies.

Cohen’s lawyer, Lanny Davis, insists his client “wants to tell the truth” about his 12-year association with the property mogul turned reality TV star and others like Omarosa Manigault appear to have stories to tell.

As The Independent’s Sean O’Grady has suggested, the upcoming mid-term elections in November could effectively serve as a referendum on whether or not to press ahead with impeachment proceedings – much more likely if the Democrats were to gain ground in the Senate, where the Republicans currently hold 51 seats to their 46.

Have there been previous attempts to impeach Donald Trump?

Yes. Last November, six House Democrats moved to have the president impeached on five articles, the most significant being his firing of FBI director James Comey in May, which they regarded as an obstruction of justice into the bureau’s ongoing Russia investigation.

The Democrats also cited violation of the Constitution’s foreign and domestic emoluments clause, barring a president from receiving gifts from foreign governments or profiting from their office respectively, the latter targeting Mr Trump’s sprawling luxury property empire.

They also argued he had undermined democracy through his derisive comments about the courts system and persistent attacks on the free press.

However, the proposal faced an uphill battle as a result of Republican dominance of the House and failed to win the support of Democrat Leader Nancy Pelosi, who felt it was premature to pursue the matter before the FBI had concluded its Kremlin probe and because the articles had more to do with personal dislike of the president than hard facts.

Has any president ever been removed from office by impeachment?

No American president has, to date, ever been removed from office through the impeachment and conviction process.

Launching proceedings against a president is a complex business and promises to throw the government into disarray, dominating the media agenda for months and leaving the authority of the White House diminished, even if the defendant were eventually acquitted.

Andrew Johnson was impeached in 1868 over his removal of secretary of war Edwin McMasters Stanton in violation of the Tenure of Office Act but acquitted thanks to his having the sound support of a Democratic majority.

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Richard Nixon resigned in disgrace in the face of imminent impeachment proceedings by the House over the Watergate scandal, preventing the need for setting them in motion.

Bill Clinton was impeached in 1998 on grounds of perjury before a grand jury and obstruction of justice as a result of his attempts to conceal an affair with White House intern Monica Lewinsky.