Donald Trump's presidency could be under threat after the US Democratic Party prepare to bring the impeachment inquiry to the Senate over allegations he asked a foreign country to investigate a political rival.
Mr Trump admitted he had spoken to Volodymyr Zelensky about Mr Biden but denied putting pressure on the Ukrainian president.
So how does impeachment work - and what could happen to Mr Trump?
What is impeachment?
As sitting presidents cannot be indicted, impeachment is a final check on the president's power.
It is a process where they are removed from their position - following a trial - and potentially barred from public office in future.
It can be used to remove presidents, vice presidents and senior civil officials such as judges who have gone rogue.
What crimes can lead to impeachment?
Impeachment proceedings are a rare occurrence in the US - something of a last resort.
The US constitution states the president can be impeached and removed from office for "treason, bribery or other high crimes and misdemeanors".
This definition, and the behaviours that are deemed to have reached that threshold are therefore open to interpretation.
How does it work?
First, the House of Representatives - the lower chamber of Congress - must pass an Article of Impeachment by majority vote.
Once this passes, there is a trial in the Senate - the upper chamber of Congress - with the Chief Justice presiding in presidential cases.
The 100 senators are the jurors, they must decide whether the president is guilty of treason, bribery, or other high crimes or misdemeanours.
For the president to be removed from office there needs to be a 'super-majority' (two thirds) of Senators voting in favour.
Fifty-three members of the Senate are Republican.
Who's been impeached before?
Only two sitting presidents have actually had the Article of Impeachment passed in the House of Representatives.
In 1868, Andrew Johnson was impeached after he illegally removed his Secretary of War, sending rising political tensions over boiling point.
The Senate needed 36 votes for guilty to get the super-majority. Johnson escaped by the skin of his teeth with 35 finding him guilty.
More recently, Bill Clinton was impeached in 1998 following the Monica Lewinsky scandal.
He faced two charges, one for perjury and one for obstruction of justice.
The super-majority requirement was 67 but he was acquitted, with the charges only getting 45 and 50 guilty votes respectively.
In fact, no president has ever been removed from office by the actual process of impeachment.
The one who probably came closest to that fate was Richard Nixon, who resigned in 1974 before impeachment proceedings could begin, and would have most likely removed him from office.
Could Donald Trump actually be impeached?
The threat of impeachment has been a running theme throughout Mr Trump's presidency.
However now that a formal investigation by the US Democrats has been launched, it poses a more realistic prospect.
Trump has called the latest impeachment talks "presidential harassment" and labelled them a "witch hunt".
Earlier during his reign, Robert Mueller's investigation into links between the Trump campaign team and the Kremlin were investigated, but Mueller didn’t find enough evidence that the Trump campaign had conspired with the Russian government.
Former CIA director John O Brennan called Trump's performance during his summit with Russian president Vladimir Putin "nothing short of treasonous", saying it "exceeds the threshold of high crimes and misdemeanours".
Questions about Trump's presidency were also raised after the Stormy Daniels' accusations against him.
Sol Wisenberg, who conducted grand jury questioning of Bill Clinton during the Whitewater investigation, said: “The stuff on Stormy Daniels is not good for Trump.
“I’m assuming he’s not going to be indicted because he’s a sitting president. But it leads him closer to ultimate impeachment proceedings, particularly if the Democrats take back the House.”
Trump’s former chief strategist Steve Bannon had previously warned Democrats could pursue impeachment proceedings if they won the midterm elections.
Now Donald Trump faces all of the drama and the theatre of impeachment, will he survive that ultimate test set by the founders 232 years ago?