The firing of Federal Bureau of Investigation director James Comey has fuelled controversy over alleged Russian involvement in the 2016 presidential election campaign - which the FBI has been investigating.
Democratic politicians, in particular, have stepped up calls for a special prosecutor to take over the bureau's investigation.
A special counsel would have to be appointed by the attorney-general or deputy attorney-general, or by the president himself.
The practice was started during the presidency of Mr Richard Nixon - who ended up firing his own appointee - in the 1970s and continued until the late 1990s with long-drawn-out investigations into the Clintons. After 1999, it fell into disuse.
A special congressional committee may be more likely, and could get support from the Republicans as well.
The New York Times quoted Republican Senator John McCain saying that President Donald Trump's decision was disappointing, and bolstered the case for a "special congressional committee to investigate Russia's interference in the 2016 election".
Mr James Comey says the Federal Bureau of Investigation (FBI) will not recommend criminal charges against Mrs Hillary Clinton for her use of a private e-mail server when she was secretary of state, but calls Mrs Clinton and her staff "extremely careless" in handling classified material.
Then candidate Donald Trump and many Republicans blast his decision.
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Events that led to Comey's sacking
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JULY 5, 2016
Some time in the same month, the FBI quietly opens a probe into Russian interference in the US election, which would be officially revealed only eight months later.
OCT 7
US intelligence officials announce that top Russian officials are behind hacking and disinformation operations designed to disrupt the election.
OCT 28
Mr Comey sends a letter to congressional leaders informing them of the existence of e-mails pertinent to the Clinton probe.
Law enforcement officials had earlier seized a laptop, phone and tablet belonging to Mr Anthony Weiner, who was under probe for alleged inappropriate communications with a minor. They discovered the laptop contained e-mails from Mrs Clinton and her aide, Ms Huma Abedin.
NOV 6
Mr Comey says the FBI has concluded it found nothing to alter its original opinion that it would seek no charges against Mrs Clinton.
NOV 8
Mr Trump wins the election.
JAN 6, 2017
Mr Comey and three other top intelligence officials brief Mr Trump on their conclusion that Russian President Vladimir Putin was behind the bid to interfere with the election, in support of Mr Trump.
JAN 18
President-elect Trump informs Mr Comey that it is his intention to keep him on as FBI director.
MARCH 20
Mr Comey confirms the FBI is investigating any links between the Trump election campaign and the Russian government. On the same day, he refutes Mr Trump's claims that the Obama administration wiretapped Trump Tower.
MAY 2
Mr Trump tweets: "FBI Director Comey was the best thing that ever happened to Hillary Clinton in that he gave her a free pass for many bad deeds!"
MAY 3
Mr Comey testifies before the Senate Judiciary Committee about his decision to announce the reopening of the probe into Mrs Clinton and her e-mails.
On May 8, a report emerges stating that he exaggerated the number of e-mails Ms Abedin forwarded to Mr Weiner.
MAY 9
The FBI clarifies that Mr Comey misspoke about the number of e-mails forwarded. Mr Trump fires him, citing recommendations from Attorney-General Jeff Sessions and Deputy Attorney-General Rod Rosenstein.
SOURCE: WASHINGTON POST, AGENCE FRANCE-PRESSE
Meanwhile, the FBI's probe into alleged Russia links, focused on figures in the Trump campaign, will continue, White House deputy spokesman Sarah Huckabee Sanders told CBS News. Until the President nominates a new FBI director, the probe would be overseen by deputy director Andrew McCabe.
Mr Comey was fired on grounds that he had lost public credibility, as well as the confidence of his staff.
"There is… a long list of reasons," Ms Sanders insisted.
The issue in the hyper-partisan environment is the timing. President Trump, who has angrily dismissed the allegations of Russian involvement as fabrications amplified by "fake news media", had not only praised Mr Comey, but also could have fired him much earlier.
"President Trump not very long ago praised Mr Comey for his handling of the Clinton e-mails," Professor Glenn Altschuler, an expert on American Studies at Cornell University, told The Straits Times (ST).
"This raises questions whether or not the reason for the firing is the probe into the Trump campaign's links with the Russians."
CNN reported that the FBI plans to issue subpoenas over its investigation of former general Mike Flynn, Mr Trump's initial pick for national security adviser, who resigned when it was revealed that he had misled Vice-President Mike Pence over the extent of his contacts with figures in the Russian establishment.
In an e-mail, Professor Inderjeet Parmar of City, University of London, wrote: "Whatever the reason, its timing… adds fuel to the fire that there is a cover-up going on, which the FBI threatened under a stubborn and independent director."
In an e-mail bulletin, security consultancy Soufan Group wrote that the fallout from Mr Comey's termination may cause profound damage to the government, given the partisan environment.
"The ultimate impact of Comey's firing on government accountability and the integrity of independent federal law enforcement rests on whether Congress can find ways to address the myriad issues stemming from Comey's dismissal in a non-partisan and collaborative manner" the Soufan Group said.
White House adviser Kellyanne Conway said on CNN the morning after Mr Comey was fired: "Almost everyone agrees the director made serious mistakes.
"This is a president who saw an FBI director who had lost public confidence."
Cornell's Prof Altschuler told ST: "The likelihood of appointing an independent counsel is not very high; President Trump has shown a proclivity for brazening it out."
