Deputy attorneys general are usually little known figures in America. Rod Rosenstein, as the man who oversees a federal investigation into possible Russian interference in the 2016 US election, and whether Donald Trump's campaign was complicit, is the rare exception.
So when reports surfaced on Monday that Mr Rosenstein had resigned or was about to be fired it was enough to raise questions about the future of the inquiry, as well as what it meant for Mr Trump's position in the White House. With Mr Rosenstein's position unclear, a meeting between the two men is scheduled on Thursday.
"Any effort to remove Rosenstein should be seen as an effort to subvert the independence of rule of law in America," wrote Brian Klass, political scientist at University College London and a Washington Post columnist.
Questions about Mr Rosenstein's future follow more than a year of turbulence and allegations of obstruction, ever since Jeff Sessions, the attorney general, announced that he was standing aside from the probe after admitting he had not been transparent about contacts with Russian officials.
At the centre, however, stands Mr Rosenstein, a 53-year-old registered Republican from Philadelphia, who now lives in Bethesda, the leafy suburb that is home to many from the Washington elite, just a few miles from the White House.
Mr Rosenstein's political credentials are not in question or, arguably, a factor. What is germane is his official authority to dismiss Robert Mueller, the special counsel and former head of the FBI who heads the Russia probe.
Mr Mueller has said he would not follow an "unlawful" order from Mr Trump to fire Mr Mueller, whose inquiry has been repeatedly condemned by the president as a witch hunt.
Speculation about the deputy attorney general's future has led allies of Mr Trump to start floating the idea that Mr Rosenstein's resignation or removal should mark a pause – or even end – the Russia investigation.
In response, Democrats in the US Congress are reviving arguments that a new law is needed to protect Mr Mueller from dismissal.
What seems to have landed Mr Rosenstein at the White House is a New York Times report that he had suggested secretly recording the president and discussed ousting Mr Trump from office using the 25th Amendment.
Republicans have long warned Mr Trump that firing his deputy attorney general could prompt impeachment on the grounds of obstruction of justice.
However Ric Simmons, a former prosecutor and professor of law at Ohio State University, said the report has given the president political cover to dismiss a deputy attorney general.
"He has always had the right to fire him but political considerations have stopped him from doing so, but those are now somewhat – or a lot – mitigated," he said, before adding that the approaching midterm elections – Americans vote on November 6 – could yet make Mr Trump hold fire for fear of pushing undecided voters to the Democrats.
Such a theory, however, does not take account of Mr Trump's temperamental character and track record for taking delight in overturning norms and confounding expectations.
Legal experts disagree about what would come next and the extent to which Mr Trump could hand pick Mr Rosenstein’s successor.
Either way it would likely herald a period of deep uncertainty for the Mueller probe.
How it plays out could depend on overlapping laws and the likelihood of Senate confirmation.
On the one hand, the Department of Justice's own order of succession could determine what happens in the event of a vacancy. That would mean Noel Francisco, the solicitor general, would be charged with taking over the Mueller investigation, skipping the department’s number three who has not yet been confirmed by the Senate.
He has in the past argued against the need for special counsels and favoured affording the president broad executive powers – something Mr Trump would approve of.
But some advisers suggest he may have to recuse himself from the investigation as his former law firm, Jones Day, represented the Trump campaign.
That would leave Steven Engel, the assistant attorney general in charge of the Justice Department's office of legal counsel, next in line.
Alternatively, Mr Trump may try to use the Vacancies Act, which affords the president the power to temporarily fill posts for 210 days until he has to submit a nomination. Such a step would expand his ability to parachute in his preferred candidate.
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Such a course though would almost certainly be challenged, according to Professor Simmons, if Mr Rosenstein were fired rather than "dies, resigns, or is otherwise unable to perform the functions and duties of the office" as the act has it.
Robert Shapiro, professor of political science at Columbia University, said the president would not get it all his own way and would still have to win Senate confirmation.
"He'll be able to pick a person more to his liking," he said. "But in terms of picking anyone who would want to close the Mueller investigation... that's a stretch."
Even so, Trump loyalists smell blood and are preparing to demand a pause in the Russia investigation.
"If in fact Rod Rosenstein does end up resigning," said Jay Sekulow, Mr Trump’s attorney on his own radio show, "I think it clearly becomes necessary and appropriate...that there be a step back taken here, and a review, a review that has to be thorough and complete... and basically a time out on this inquiry."
That may not be enough to end the scrutiny of Mr Trump, his campaign and their Russian contacts.
Prof Simmons said he had faith that the investigation would continue in one form or another. Mr Mueller had already obtained enough evidence, he added, for others in the Department of Justice to continue his work.
"Some federal prosecutors around the country are already looking at this. So it's hard to imagine that it is stoppable in any meaningful way," he said. "You can't just fire Mueller and expect it to go away."
