The firing of FBI Director James B. Comey brought to a stunning conclusion one of the most controversial chapters in the bureau’s modern history. But its timing raised fresh and potentially troublesome questions about the future of the investigation Comey was overseeing into possible links between associates of President Trump’s campaign and the Russian government.

There was a certain irony to the explanation offered for the dismissal, which was focused on Comey’s handling of the investigation into Hillary Clinton’s emails. Many Democrats, including Clinton, believe what Comey did by reopening the investigation late in the campaign contributed to Trump’s victory last November. That’s one reason that, by the time of his dismissal, Comey had few public advocates and many detractors for his actions and his unwillingness to concede error.

That might explain why Trump’s order to fire Comey produced, initially at least, a somewhat muted reaction among elected officials in both parties, or at least reactions that offered no clear defense of the FBI director.

But as the hours passed and the shock of the announcement rippled more widely, Democrats and some Republicans began to raise concerns about the timing and therefore the possible implications of the action by a president whose administration has been clouded since its very start by the Russia investigation, with any number of Democrats accusing Trump of an abuse of power.

(Bastien Inzaurralde/The Washington Post)

Those concerns about what could happen to the investigation into Trump’s campaign and the Russians were summed up most succinctly in a tweet by Robby Mook, the campaign manager for Clinton, who said, “Twilight zone. I was as disappointed and frustrated as anyone at how the email investigation was handled. But this terrifies me.”

The shock of the firing brought back immediate comparisons to the 1973 Saturday Night Massacre during the Watergate scandal, ordered by then-president Richard M. Nixon. Those firings generated an immediate firestorm and a powerful backlash against the embattled president, one step along the way to eventual impeachment proceedings and resignation from office.

In that case, the attorney general refused to carry out Nixon’s orders to fire the Watergate special prosecutor. In this case, Trump said he had acted on the recommendation of Attorney General Jeff Sessions and newly installed Deputy Attorney General Rod Rosenstein.

It was Rosenstein, a career prosecutor, who laid out the bill of particulars against Comey in a memorandum to Sessions. He was unsparing in his criticism of Comey’s handling of that matter, noting, “My perspective on these issues is shared by former attorneys general and deputy attorneys general from different eras and both political parties.”

He said the FBI director had overstepped his authority and compounded the mistake by holding a news conference last July 5 in which he announced that he would not seek prosecution but during which he was sharply critical of Clinton. He was equally critical of Comey’s decision to announce in a letter to Congress last Oct. 28 that he was reopening the investigation, which Clinton’s advisers believe was a contributing factor to her loss to Trump in November.

Rosenstein also said Comey was wrong to defend his actions, as recently as last week during testimony before a congressional committee. He ended by asserting, “The FBI is unlikely to regain public and congressional trust until it has a director who understands the gravity of the mistakes and pledges never to repeat them.”

Many Democrats would agree with the case Rosenstein laid out to justify Comey’s firing, and yet there were as many questions about why now and what finally triggered an action that is virtually without precedent. That a president whose campaign is under investigation would dismiss the official leading the investigation naturally evokes suspicions and concerns about the true motives behind the action.

This, after all, is not the first Justice Department official removed by the president. Early in his term, Trump dismissed the then-acting attorney general, Sally Yates, who had declared that the Justice Department would not defend the president’s initial travel ban executive order. Not much later, Preet Bharara, the former U.S. attorney for Manhattan, was fired after refusing a White House directive to resign.

The pattern and practice has fueled alarm among Democrats. Sen. Patrick J. Leahy (D-Vt.), a former chairman of the Senate Judiciary Committee, dismissed as “a fig leaf” the explanation that Comey was being fired for his handling of the Clinton investigation, arguing that it was a deliberate effort to impede an investigation that could severely damage his administration. “This is nothing less than Nixonian,” he said in a statement.

The firing of Comey has left the administration once again in a quandary about how to proceed with respect to the investigation into the Trump campaign and the Russians. The administration long has resisted such a course, but in the wake of Tuesday’s stunning moves, the president, the attorney general or the deputy attorney general will be called on to reassure the public that the investigation will continue as aggressively as it would have without a change in leadership at the bureau.

Meanwhile, Trump will be under pressure to yield to calls for a special prosecutor to take over the case, a decision that might create greater confidence in the independence of the investigation but that the president and his allies might see as a potentially more perilous course. It was notable that in his brief letter of dismissal to Comey, he went out of his way to declare that the FBI director had told him three times that he was not under investigation.

The president has tried to wish away the questions about possible collusion or cooperation between associates of his campaign and the Russians during last year’s election. He has been reluctant to accept, firmly, the conclusions of the intelligence community that the Russians interfered in the election with the purpose of hurting Clinton and therefore helping him. He has said there is no evidence of collusion.

Comey’s public statement earlier this spring that the bureau was looking into those allegations made it clear that, whatever the president said or tweeted, there was a serious investigation underway that was threatening to his administration. By dismissing Comey on Tuesday, the president has significantly raised the stakes, for the Justice Department, the FBI and ultimately his own administration, to demonstrate that the investigation will continue to its rightful conclusion without interference.