WASHINGTON (AP) -- With his shocking dismissal of FBI Director James Comey, Donald Trump is propelling the presidency into rarely traversed territory.
His surprise announcement Tuesday flouts decades of presidential deference to the nation's top law enforcement agency and its independence. It earns Trump the dubious distinction of being the first president since Richard Nixon to fire the official overseeing an investigation involving the commander in chief. And it cements a clear pattern of a man willing to challenge - in dramatic fashion - the institutions created to hold the president accountable.
"That's why this is unprecedented," said Michael Beschloss, a presidential historian. "He's showed signs of not having a great deal of respect for the system by which this investigation has been operating."
Sen. Richard Burr, the North Carolina Republican who is overseeing one of the congressional investigations into Russia's election interference, said: "I am troubled by the timing and reasoning of Comey's termination."
Sen. Jeff Flake, R-Ariz., said he'd spent hours trying to find "an acceptable rationale" for Trump's decision. "I just can't do it," he said.
Trump attained his White House goal after a decades-long career in business during which he was accountable to few people other than himself. Thus, he has chafed at the constitutionally mandated constraints on the presidency. Within days of taking the oath of office, he suddenly fired acting Attorney General Sally Yates - a career Justice Department official - after she refused to defend the White House's controversial travel and immigration ban. When the federal courts blocked that measure as well, Trump aggressively castigated individual judges as political actors and challenged the court's role in curbing a president's policies.
No matter which president originally appoints them - Comey was tapped by Barack Obama in 2013 - almost all FBI directors are allowed to serve out their full 10-year terms under successor commanders in chief. Bill Clinton is the only other president to fire an FBI chief, amid questions about the director's use of FBI aircraft for personal purposes.
The Trump White House cited Comey's handling of last year's investigation into Hillary Clinton's email practices as the cause for the firing, and, to be sure, Comey left himself vulnerable.
He was widely criticized for heavy-handed and high-profile decisions in the case, particularly when he sent a letter to Congress 10 days before the election saying the bureau was looking at new information related to the inquiry. He said at the time that the new information related to emails found on a laptop belonging to the husband of Clinton aide Huma Abedin, the disgraced congressman Anthony Weiner.
At the time, Trump praised Comey for having "guts" and doing "the right thing," statements that complicate his assertion that now, seven months later, Comey's decisions warranted firing.
Trump's announcement came as Comey was again facing criticism, this time for telling congressional lawmakers that Abedin had forwarded "hundreds or thousands" of emails to the laptop. On Tuesday, hours before Trump fired Comey, the FBI told lawmakers that the director was wrong, and Abedin had forwarded only a "small number" of emails.
Although Democrats blame Comey for Clinton's loss, they are unlikely to accept Trump's explanation for the firing.
The president has repeatedly dismissed Comey's Russia investigation - as well as the congressional inquiries - as a "hoax." He's also insisted that he is not personally under investigation - asserting Tuesday that Comey told him three times that he was not a target - though the FBI has stated unequivocally that the president's campaign and his associates are facing scrutiny.
"This is Nixonian," said Sen. Bob Casey, D-Pa.
Jimmy Gurule, a former assistant attorney general who was appointed by President George H.W. Bush, said Trump's decision "threatens our democracy and undermines the integrity of the FBI investigation." Gurule is now a law professor at the University of Notre Dame.
Nixon's decision had a ripple effect throughout his administration, with the attorney general and deputy attorney general resigning rather than carry out the president's orders. There was no such response from Trump's White House aides and other top administration officials.
"We haven't had a voice from within the Trump administration denounce this yet," said Douglas Brinkley, a presidential historian at Rice University. "I think at this moment the question is, will leading Republicans step out of the box and become profiles of courage?"
In the immediate aftermath of Trump's announcement, many Republicans appeared more inclined to back his decision, citing their own concerns with Comey's stewardship of the FBI following months of controversy.
None of the Republicans who did raise concerns were rushing to draw comparisons to Nixon, the only president to resign from office. Yet they, too, appeared troubled by Trump's decision and wary of the prospect of White House interference in an investigation involving the president.
Comey's "removal at this particular time will raise questions," said Sen. Bob Corker, R-Tenn. It is essential, he said, that ongoing investigations are full "and free of political interference until their completion."
Julie Pace has followed the White House and politics for The Associated Press since 2007. Follow her at http://twitter.com/jpaceDC
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