President Donald Trump abruptly fired FBI Director James Comey, ousting the nation's top law enforcement official in the midst of an investigation into whether Trump's campaign had ties to Russia's election meddling. Picture: Carolyn Kaster/AP

Washington — President Donald Trump's firing of FBI Director James Comey throws a cloud of doubt over the bureau's investigation into allegations of Trump campaign ties to Russia.

The FBI and three congressional committees have been investigating Russia's interference in the 2016 election and possible Trump connections. As head of the FBI, Comey had been leading the complex counterintelligence investigation that has dogged the Trump White House since Inauguration Day.

The White House said Tuesday its search for a new FBI director had already begun. And the person Trump appoints will likely have a huge impact on how the investigation moves forward and whether the public will accept its outcome. But given concerns by members of Congress in both parties over Comey's dismissal, it's unlikely a permanent director will be in place soon.

A new director chosen by Trump could decide to drop the FBI investigation altogether, or not pursue it as aggressively as Comey has. He or she could also decide not to fully cooperate with the congressional investigations, which rely on information from the FBI.

Timothy Flanigan, a former assistant attorney general in the George W Bush administration, said, "It does seem to me, however, that, if investigations are underway, they will likely continue." He said acting FBI directors have limited abilities to derail an ongoing investigation.

Still, Democrats immediately pushed to try to ensure the evidence collected so far was preserved.

In a letter to the FBI and the Justice Department, six Democrats on the House Judiciary Committee asked the agencies to preserve all records related to the probe and to Comey's firing.

That is needed to "protect the integrity" of the investigation, the Democrats wrote.

Trump said his decision to fire Comey had nothing to do with Russia. But the impact of removing an independent FBI director who was leading an investigation with potentially dire ramifications was not lost in the dramatic removal of the nation's top law enforcement official.

"I am troubled by the timing and reasoning of Director Comey's termination," Senator Richard Burr, R-N.C. said in one of the strongest statements from a Republican. As chairman of the Senate intelligence committee, Burr is leading one of the three congressional investigations and has been in regular contact with Comey.

"His dismissal further confuses an already difficult investigation by the committee," Burr said.

Comey's firing was the latest and most significant White House-driven distraction from the Russia investigations. Trump has ridiculed the probes, calling them a "hoax," and he has denied that his campaign was involved in Russia's election meddling. In his brief letter to Comey, Trump thanked him for telling him three times "that I am not under investigation."

The FBI has not confirmed that Comey ever made those assurances to Trump. In public hearings, Comey has declined to answer when asked if the president was under investigation, urging lawmakers not to read anything into that statement.

But it's hard to see Comey's firing as anything other than political, said Frank Montoya Jr., a former FBI agent who worked on counterintelligence investigations and led the bureau's Seattle office. Montoya said other counterintelligence investigations were important but never got the level of attention that the Russia investigation has.

"They were fought in the shadows. It was spy versus spy," Montoya said. He said there would be no question about the current investigation continuing if not for the political implications.

Others questioned whether Trump's actions amount to interfering in an ongoing investigation. Already, Trump's attorney general, Jeff Sessions, who was active in the Trump campaign, has recused himself.

The decision to fire Comey, "raises profound questions about whether the White House is brazenly interfering in a criminal matter," Republican Adam Schiff, D-Calif., said in a statement. Schiff is the top Democrat on the House intelligence committee, which is also investigating. Schiff and other Democrats said it is imperative that the Justice Department appoint a special prosecutor.

The executive director of the Project on Government Oversight, Danielle Brian, said Trump's move — whether or not so intended — "undermines the independence and credibility of that investigation."

"This is a deeply troubling development for our system of checks and balances and the rule of law," Brian said in a statement.

The FBI's deputy director, Andrew McCabe, was named the acting director until Trump appoints a replacement and the Senate confirms the appointment. McCabe was dragged into the spotlight of the Russia investigation in February when the White House said he disputed media reports that Trump's campaign advisers were frequently in touch with Russian intelligence agents during the election. The FBI never confirmed that McCabe and Comey gave the White House the go-ahead to knock down the stories.

While unlikely, Comey's ouster also could lead to the appointment of a special prosecutor, a recommendation Democrats have been pushing for months.

AP