The White House says Donald Trump has the power to fire special counsel Robert Mueller. But one expert believes it could lead to impeachment proceedings against the president.
For almost a year, US President Donald Trump remained uncharacteristically quiet on special counsel Robert Mueller - the man overseeing the investigation into Russian interference during the 2016 election campaign.
But that has changed dramatically in recent weeks.
On Tuesday, the White House went as far to say the president has the power to fire Mr Mueller, if he so wished.
Why the sudden fall out?
Mr Mueller's investigation got underway in May 2017 but it wasn't until last month that Mr Trump mentioned him directly.
"The Mueller probe should never have been started ... WITCH HUNT!" he tweeted.
The situation escalated further when FBI agents raided the offices of Mr Trump's longtime personal lawyer Michael Cohen at Mr Mueller's request on Monday, in relation to the investigation.
Railing against what he described as "an attack on our country," Mr Trump said "many people" were now advising him to fire Mr Mueller.
He took to Twitter again to call the investigation "A TOTAL WITCH HUNT!!!"
Could Trump be impeached?
Associate professor Brendon O'Connor from Sydney University's United States Studies Centre told SBS News Mr Trump "is itching to sack Mueller".
"He would want to believe he could get away with it. But I'm sure there's a lot of people in the White House saying 'steady on.'"
Dr O'Connor said federal regulations stipulate that only the Department of Justice can fire the special counsel.
As there's been no indication of this happening, Mr Trump could install someone more sympathetic at the department and get him or her to fire Mr Mueller.
This is similar to the route former president Richard Nixon took to fire a special prosecutor during the Watergate scandal, in order to protect himself.
Although Mr Trump's track record seems to suggest he has little regard for such procedures and could fire Mr Mueller outright.
"(But) if Trump did it himself, he's really risking the Congress looking into articles of impeachment," Dr O'Connor said.
"It would be such a dramatic decision and could clearly be seen as obstruction of justice, particularly since he already sacked former FBI director Jim Comey. There would seem to be a pattern of obstruction of justice."
What do Republicans, Democrats think?
Republicans and Democrats in Congress have warned the president of firing Mr Mueller.
"The investigation is critical to the health of our democracy and must be allowed to continue," top Senate Democrat Chuck Schumer said.
While Senate Judiciary Chairman Republican Chuck Grassley told CNN, "I think it would be suicide for the president to fire him".
But regardless of the route taken, Dr O'Connor said Democrats would quietly be "gleeful" if Mr Trump fired Mr Mueller and "see this as a great opportunity to get rid of Trump".
He said impeachment proceedings would likely be immediately discussed.
How does impeachment work?
Impeachment begins with a vote in Congress' House of Representatives. If a majority votes in favour of impeachment, the case moves to the Senate, where a two-thirds majority is required to convict and remove a president.
But both of these chambers are currently controlled by Republicans.
As such, Dr O'Connor said the firing of Mr Mueller would be a "real acid test" for Republicans in Congress.
He said these individuals would be forced to ask "if they have the spine to deal with this issue, to deal with some clear obstruction of justice - especially if it was a direct firing by Trump - or to game this out politically".
Dr O'Connor said Mr Mueller's firing would not be another regular Trump scandal, many of which he has been able to shrug off.
"(Mr Trump would be) breaking the law ... He doesn't have the authority to sack the Special Investigator, so it's different. This isn't going to be fought out in the court of public opinion … It's going to be fought out in a more procedural process."
What do we know about Mueller?
Robert Mueller is an attorney who rose up the ranks to serve as the director of the FBI from 2001 to 2013.
He was appointed as FBI chief by the Republican president George W. Bush and kept on under Democrat Barack Obama.
In May 2017, Mr Mueller was selected to head the Special Counsel investigation into Russian efforts to tip the 2016 presidential election in Mr Trump's favour.
Over the last year, he has increasingly dug into evidence of alleged money laundering, fraud and obstruction of justice inside Mr Trump's inner circle.
Four Trump aides - including his 2016 campaign chair Paul Manafort and former national security advisor Michael Flynn - have already been indicted or pleaded guilty.
Additional reporting: AFP, AAP