Once again, Donald Trump has tried to lift Moscow’s shadow off his presidency — and once again, he has done the opposite.

New questions are arising in the wake of his sudden decision to can FBI Director James B. Comey, along with revived calls for the appointment of a special prosecutor to investigate the question of Russian influence in last year’s election and the Kremlin’s connections to Trump’s presidential campaign.

“The only thing that is guaranteed right now is that the sense of chaos will continue, not only in law enforcement but also in Congress,” said GOP strategist Kevin Madden, a veteran of Capitol Hill and the Justice Department. “Every single lawmaker in the House and Senate is going to be pressured to take a stance.”

Of course, the surest way to end the controversy would be through a credible investigation that comes to a definite conclusion about the methods and extent of Russian meddling in the 2016 election and whether it involved improper dealings with people close to Trump.

“There will be no normalcy to his presidency if there is no independent investigation,” said Ron Klain, who was chief of staff in the Justice Department during the Clinton administration. “There is something absolutely essential about it but nothing inevitable about it.”

1 of 28 Full Screen Autoplay Close Skip Ad × The scene in Washington after FBI Director Comey was fired View Photos President Trump’s firing of James B. Comey consumed Capitol Hill’s attention. Democrats slowed committee business in the Senate to protest the lack of an independent investigation into Russia’s election meddling, and Republicans saw rifts emerge as more questioned the president’s decision. Caption President Trump’s firing of James B. Comey consumed Capitol Hill’s attention. Democrats slowed committee business in the Senate to protest the lack of an independent investigation into Russia’s election meddling, and Republicans saw rifts emerge as more questioned the president’s decision. May 9, 2017 White House press secretary Sean Spicer speaks to reporters outside the West Wing after President Trump dismissed James B. Comey from his position as FBI director. Jabin Botsford/The Washington Post Buy Photo Wait 1 second to continue.

When Trump fired an FBI director who was investigating his presidential campaign, “I was shocked last night, and I thought I couldn’t be shocked by anything anymore,” Madden said Wednesday. “Absent some sense of finality, members of Congress and law enforcement will have this hanging over them.”

But every out-of-the-ordinary turn seems to weaken confidence that the existing inquiries — both within the Justice Department and by the two intelligence committees on Capitol Hill — will actually be capable of producing a result widely accepted as untainted and convincing.

White House officials maintain that Comey’s firing had nothing to do with his agency’s Russia investigation but, rather, with his handling of the probe into Democratic presidential nominee Hillary Clinton’s emails.

Yet Trump’s letter terminating Comey alluded to the questions surrounding his own administration (“While I greatly appreciate you informing me, on three separate occasions, that I am not under investigation …”) and made no mention of the FBI director’s much-criticized decisions involving Clinton.

White House deputy press secretary Sarah Huckabee Sanders declined to say when and under what circumstances Comey gave assurances to the president that he was not under investigation.

Nor were the day-after optics conducive to tamping down the controversy. The only event on Trump’s publicly announced schedule was a meeting with Russian Foreign Minister Sergei Lavrov. The session was closed to the media — with the apparent exception of a photographer from Russia’s state-run news agency Tass, which lit up the Internet with its photos.

Then came another surreal turn: When reporters were summoned to the Oval Office for a brief opportunity to ask Trump questions, they found the president sitting not with Lavrov but with another visitor, former secretary of state Henry Kissinger.

View Graphic With Comey's dismissal, the Russia investigation will soon be run by Trump allies

The inopportune presence of a Watergate-era figure punctuated comparisons of Trump’s actions with Richard Nixon’s “Saturday Night Massacre” of the special prosecutor looking into the scandal that ultimately forced Nixon’s resignation.

For Republicans, the frustration and perplexity surrounding Trump’s decision to fire Comey is compounded by the fact that it comes just days after his biggest legislative victory so far: the House passage last week of legislation to begin making good on the GOP’s promise to repeal and replace the Affordable Care Act.

Reviving the Russia controversy is likely to distract not only from the Senate’s efforts to pass its own health-care legislation but also from other ambitious items on the GOP agenda, including overhauling the tax code.

“Comprehensive tax reform just got an awful lot harder, as did nearly every other challenge facing the nation, both foreign and domestic: infrastructure, health care, immigration, trade and others,” former New York mayor Michael R. Bloomberg wrote Wednesday in a column published by Bloomberg News.

In that sense, the timing is reminiscent of another episode earlier in the Trump presidency.

Four days after giving a widely praised address to Congress on Feb. 28, the president tweeted a false claim that President Barack Obama had tapped Trump’s phones “during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!”

That, too, was a reference to the investigation into links between Trump associates and the Russian government, and it exasperated Republicans who had been hopeful that the speech to Congress marked a new, more presidential turn on Trump’s part.

The debate over whether there is a need for a special prosecutor reflects doubts that the Justice Department is capable of doing its work in this highly charged political environment.

Deputy Attorney General Rod J. Rosenstein, who wrote the memo recommending Comey’s dismissal, is highly respected by both parties on Capitol Hill, though some now say he cannot continue to oversee the probe, given his role in removing the lead investigator.

“Deputy Attorney General Rosenstein now has no choice but to appoint a special counsel,” Sen. Patrick J. Leahy (D-Vt.), a senior Democrat on the Senate Judiciary Committee, said in a statement. “His integrity, and the integrity of the entire Justice Department, are at stake.”

Others disagree.

“I look at Rod J. Rosenstein, and I think who better than Rod J. Rosenstein to conduct an investigation,” said Mark Corallo, who directed public affairs at the Justice Department during the George W. Bush administration. “There are enough people at the department who can do a credible investigation. The politics of this are going to be the usual Sturm und Drang of Washington.”

It remains to be seen how the furor in Washington over Comey’s firing resonates with voters across the country.

“There aren’t a lot of great options, but making noise is the only thing that is going to bring about change,” said Richard Ben-Veniste, who was a special prosecutor during Watergate and later served on the independent commission investigating the Sept. 11, 2001, terrorist attacks. “The ‘Saturday Night Massacre’ really woke up the American public to the fact that something was going on, though the extent was not understood.”

But most Americans probably had barely heard of the FBI chief before recent months, when news reports have been filled with criticism of his decisions during the presidential campaign and since. Comey’s reputation has been so badly battered that many Americans may agree with Trump that his firing was amply justified, even amid his investigation of the Russia matter.

So it appears far from certain — or even likely — that lawmakers and administration officials will open new avenues of ­investigation.

And Trump’s unpopularity may actually reinforce his administration’s resistance to additional measures, such as appointing a special prosecutor. The polls, which give Trump a record-low approval rating for a president this early in his first term, indicate that his supporters will stick with him, while the majority in the country seems hardened against him.

“In some weird ways, having a 40 percent approval rating means never having to say you’re sorry,” Klain said. “No one’s going to walk into the Oval Office and say, ‘Your approval ratings are down,’ because his approval ratings are already down. When you’re in the basement, the fear of falling is very, very limited.”

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