WASHINGTON — Under intense pressure to ensure independence in the federal investigation into Russian interference in last year's election, Deputy Attorney General Rod J. Rosenstein appointed a special counsel Wednesday to oversee the probe — a move that ratchets up the mounting scrutiny of the increasingly embattled presidency of Donald Trump.
Rosenstein, who until last month was the U.S. attorney in Maryland, named former FBI Director Robert S. Mueller III to take over the investigation, and expressly charged him with looking into whether there was any coordination between the Russian government and Trump's presidential campaign.
"Based upon the unique circumstances, the public interest requires me to place this investigation under the authority of a person who exercises a degree of independence from the normal chain of command," Rosenstein said in a statement. "I determined that a special counsel is necessary in order for the American people to have full confidence in the outcome."
He stressed that his decision was not a finding that crimes had been committed or that any prosecution was warranted.
The decision came as Democrats and a growing number of Republicans on Capitol Hill have become increasingly critical of the president's interactions with FBI Director James B. Comey, whom he fired last week.
White House officials have repeatedly denied that the president did anything wrong and have framed questions about Russian involvement in the election as politically motivated.
Trump sounded that refrain earlier Wednesday in a commencement address at the U.S. Coast Guard Academy in Connecticut, saying that "no politician in history — and I say this with great surety — has been treated worse or more unfairly."
Hours later, after Rosenstein announced the special counsel, Trump said there was no collusion between his campaign and any foreign entity. "I look forward to this matter concluding quickly," Trump said in a statement. "In the meantime, I will never stop fighting for the people and the issues that matter most to the future of our country."
But the appointment of a special counsel, with the authority to issue subpoenas and prosecute federal crimes, could fundamentally change the course of Trump's administration, even if Mueller finds no wrongdoing.
Special investigations into the Iran-Contra affair during the Reagan administration and the Whitewater controversy during the Clinton administration took over the nation's capital, diminishing the ability of the White House to advance its agenda.
Trump, only four months in his term, is already struggling on that front.
The latest political storm, coupled with the still-potent fallout from Trump's recent disclosure of classified information to Russian diplomats, is already overshadowing all else in Washington. Stocks fell sharply on Wall Street as investors worried that the latest turmoil in Washington could hinder Trump's pro-business agenda.
Rosenstein is no stranger to the highly sensitive investigations led by special counsels. He was associate independent counsel under Kenneth W. Starr during the Whitewater probe. He left for the U.S. attorney job in Maryland before the examination turned toward President Bill Clinton's affair with intern Monica Lewinsky.
Mueller led the FBI from 2001 to 2013, a tenure second in length only to that of FBI founder J. Edgar Hoover. Like Rosenstein, who was appointed U.S. attorney by Republican President George W. Bush and asked to stay on by Democratic President Barack Obama, Mueller's directorship spanned presidential administrations of both parties.
Rosenstein and Mueller, both Republicans, have developed a reputation for being apolitical, winning them bipartisan support in Washington.
For Rosenstein, that standing was put to the test when the White House released a three-page memo he crafted last week that laid out the administration's justification for firing Comey. Rosenstein criticized Comey's public declarations during the presidential campaign last year on the FBI investigation into Democratic nominee Hillary Clinton's use of a private email server as secretary of state.
The White House initially said the president relied on Rosenstein's recommendation to make the decision, but Trump himself later said he would have fired Comey anyway.
The inconsistencies in the White House accounts of Comey's firing, and the appearance that Trump had repeatedly leaned on the FBI director over the Russia investigation, only intensified calls for a special counsel, also known as a special prosecutor.
The announcement Wednesday evening won praise from Democrats and a more muted response from many Republicans.
Senate Majority Leader Mitch McConnell said a probe by the Senate Intelligence Committee would continue. House Speaker Paul Ryan said he welcomed Mueller's new role.
Rep. Andy Harris, Maryland's only Republican congressman, said he supported Rosenstein's move.
"Just as I agreed with Deputy Attorney General Rosenstein's assessment that Mr. Comey damaged the credibility of the FBI, I trust his judgment in appointing a special counsel to lead the investigation into potential interference by Russia in our 2016 election," the Baltimore County lawmaker said in a statement.
Mueller, Comey's immediate predecessor, might be best known in Baltimore for leading an NFL probe into domestic violence allegations against Ravens running back Ray Rice. He issued a report in early 2015 finding that the team should have been more forthcoming to the league with information.
In this case, Rosenstein wrote in the order naming him to the position, Mueller will have broad authority to "ensure a full and thorough investigation of the Russian government's efforts to interfere in the 2016 presidential election."
Rep. Elijah E. Cummings of Baltimore, the top-ranking Democrat on the House Oversight and Government Reform Committee, accused Republicans earlier Wednesday of slow-walking congressional investigations into the election.
Later, he lauded Rosenstein and Mueller. "Knowing Deputy Attorney General Rosenstein from his tenure in Baltimore, I think he made a solid choice in Mr. Mueller, and I commend him for putting our country and justice system first," Cummings said. "I urge Mr. Mueller to follow the facts wherever they may lead — with integrity and independence."
Rep. C.A. Dutch Ruppersberger, a former county prosecutor, agreed. "I never had any doubt of Rosenstein's integrity or independence," the Baltimore County Democrat said. "Now the American people can feel secure that we can move forward with this investigation without any undue influence from the White House."
Rosenstein, 52, developed a reputation for largely avoiding in politics in Maryland, and he won Senate confirmation last month on a nearly unanimous vote.
But Democrats became critical of him after the White House used his memo to justify Comey's firing at a time he was leading the Russia probe. Just weeks after voting for his confirmation, some Democrats called for him to appoint a special prosecutor or step down.
"His choice of Robert Mueller was solid and shows the seriousness Mr. Rosenstein brought to this decision," Sen. Ben Cardin of Maryland said in a statement. "Rather than 'make this go away,' Deputy Attorney General Rosenstein has taken an important step toward restoring the credibility of the DOJ and FBI in this most serious matter."
Questions about Trump's conduct have been mounting for weeks, most recently with two explosive allegations — that in February the president pressed Comey to drop a federal investigation into ousted national security adviser Michael Flynn's contacts with Russia and that he disclosed classified information to the senior Russian officials last week.
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Both allegations came from anonymous sources, and the White House was quick to denounce the leaks and deny any impropriety, insisting that the president never tried to squelch the Flynn investigation or made inappropriate disclosures to the Russians.
Trump is preparing to leave town Friday on his first foreign trip. Aides have been hopeful the journey will be a chance for the administration to get back on track after weeks of chaos and distractions.
Republican Sen. Lindsey Graham of South Carolina speculated Trump was probably happy to get out of town — "and a lot of us are glad he's leaving for a few days."
His advice to the president: "Stay disciplined, stay focused and deliver on the world stage."
The Associated Press contributed to this article.