After the attack on Congress by a pro-Trump mob, there are growing calls for the president to be removed for “inciting” the riot.
Donald Trump, a Republican, is due to leave office just days from now, on 20 January, when Democrat Joe Biden will be sworn in.
But Democrats, including House of Representatives Speaker Nancy Pelosi, want Mr Trump to be held responsible for actions which many say prompted the 6 January riot.
Even though it may be too late to remove him before the end of his term, they are still keen to sanction him.
So what is President Trump up against?
To impeach means to bring charges in Congress that will form the basis for a trial. It’s important to note this is a political process, rather than a criminal one.
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”.
Democrats are likely to push for a vote later on Wednesday in the House of Representatives.
The president has already been impeached over allegations he sought help from Ukraine to boost his chances of re-election. The Senate acquitted him of these charges.
Now, Mr Trump could become the first president in history to be impeached twice.
For that to happen, impeachment (charges) must be brought to the House and passed in a vote.
The case is then passed to the Senate, where a two-thirds vote is necessary to convict the president and remove him from office. It is unclear if Democrats would get those numbers in the Senate, where they only hold half of the seats.
If convicted, Mr Trump would also lose benefits granted to his predecessors under the 1958 Former Presidents Act, which include a pension and health insurance. He could also lose a lifetime security detail at taxpayers’ expense, although experts say it is unclear if this would happen.
If Mr Trump were to be convicted, the Senate could also hold a further vote to bar him from holding public office again.
A memo from an aide to Senate Republican leader Mitch McConnell says the soonest the upper chamber could take up any articles of impeachment from the House would be on 19 January, the day before Mr Trump’s term expires.
The document says Senate rules mean the chamber could therefore not begin a trial of Mr Trump until one hour after he had left office, or a day later.
But senior House Democrats say that the party may choose not to send any articles of impeachment to the Senate until after Mr Biden’s first 100 days in office.
That would allow Mr Biden to confirm his new cabinet and kick-start key policies including tackling coronavirus – something that would have to wait if the Senate had already received the impeachment articles.
Constitutional experts are split on whether impeachment can proceed to a Senate trial after a president has left office.
Read more: Impeachment: A very simple guide (Written December 2019)
The 25th Amendment
The top congressional Democrats – Speaker Pelosi and Senate Democratic leader Chuck Schumer – had urged Vice-President Mike Pence to invoke the 25th Amendment that would allow him and the Cabinet to strip Mr Trump of his powers for “his incitement of insurrection”.
On Tuesday night the House passed a resolution almost entirely along party lines urging the vice-president to invoke the 25th Amendment and “declare what is obvious to a horrified nation: That the president is unable to successfully discharge the duties and powers of his office.”
However, in a letter to Ms Pelosi hours earlier, Mr Pence had said he was unwilling to do so.
“I do not believe that such a course of action is in the best interest of our nation,” he wrote.
The 25th Amendment allows the vice-president to become acting president when a president is unable to continue his duties, if for example, he or she becomes incapacitated due to a physical or mental illness.
Could Trump pardon himself?
Media reports, quoting unnamed sources, say Mr Trump has suggested to aides he is considering granting a pardon to himself in the final days of his presidency.
The president already faces numerous investigations, including New York State inquiries into whether he misled tax authorities, banks or business partners.
So could the president pardon himself?
The short answer is we do not know, given the short wording but broad application of the constitution, and the fact there is no precedent for a US leader issuing such a pardon.
Some legal experts have previously said no, citing an opinion issued by the Justice Department days before Richard Nixon’s resignation that he could not pardon himself “under the fundamental rule that no-one may be a judge in his own case”.
Others though say the constitution does not preclude a self-pardon.
How likely is any of this?
A number of senior Republicans have said they will support a second impeachment, making a vote in favour in the House all the more likely.
However, the question is whether the required two thirds of the Senate would vote to remove the president. At least 17 Republican senators would have to vote for conviction.
According to the New York Times, as many as 20 Senate Republicans are open to convicting the president, but the timeline of when a trial could be held is not known.
As for invoking the 25th Amendment, this appears to have been ruled out.