Kevin Johnson, and David Jackson

USA TODAY

WASHINGTON — In business and now in politics, Donald Trump has proved himself time and again extraordinarily adept at vanquishing all comers.

His unlikely path to the White House is littered with would-be political challengers, whom he tattooed with disparaging monikers such as “Lyin' Ted Cruz’’ or “Crooked Hillary.’’ And of course, the real estate mogul is virtually synonymous with the catchphrase, "You're fired!"

But by firing the FBI director — who was running an ongoing investigation into possible collusion between his campaign associates and Russia — Trump has unleashed a formidable rival who may finally outdo him.

An untethered James Comey is now the single greatest threat to his young administration.

Explosive revelations that Comey maintained secret files of his encounters with Trump, including a February meeting in which the president pressed Comey to shut down the FBI investigation of former national security adviser Michael Flynn, gives Comey even more power than he had as FBI director.

"I think the president wildly underestimated Comey and the organization of the FBI," said Ron Hosko, a former FBI assistant director who worked with Comey. "Jim Comey represents a huge challenge to the viability of this president."

The bureau’s wide-ranging inquiry into Russia’s intervention is not close to completion, but less than 24 hours after the existence of the former director’s personal files was made public, the news sent a shiver through Congress unlike any of the recent crises that have engulfed the White House.

Lawmakers are now clamoring for Comey's notes or any recordings of the private conversations. At least four congressional committees — Senate Judiciary, Senate Intellingence, House Intelligence and House Oversight — have either requested documents, threatened subpoenas, or signaled that they will.

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As Democrats raise the specter of possible "obstruction of justice'' and impeachment, House Speaker Paul Ryan, R-Wis., early Wednesday acknowledged that a new congressional inquiry was necessary to understand the gravity of the Comey memos. (The intelligence committees in the House and Senate already are investigating Russia's interference in the 2016 election.)

Utah Rep. Jason Chaffetz, the Republican chairman of the powerful House Oversight and Government Reform Committee who is leading the new probe, immediately offered a daunting assessment of the panel's new responsibility.

"If true, these memoranda raise questions as to whether the president attempted to influence or impede the FBI's investigation as it relates to Lt. Gen. Flynn,'' Chaffetz said in a letter requesting that the FBI provide the former director's notes by next Wednesday. Chaffetz has signaled he would be willing to subpoena the documents if necessary, and he has scheduled a May 24 hearing, though it was not clear whether Comey had committed to appearing.

The Senate Intelligence Committee on Wednesday requested that the former FBI director appear before its panel in public and closed sessions to discuss his contacts with Trump. The panel also requested testimony of acting FBI Director Andrew McCabe related to “any notes or memorandum prepared by the former director.’’

Once Comey's notes are in the hands of lawmakers, they are likely to feel pressure to take action.

"Based on what I know about Jim Comey, he was making notes about his meetings with Trump as soon as he got in the car or off the phone," Hosko said. "And if the president thought he was going to use his charm to sway the focus of the Russia investigation, then he was very much mistaken."

The source who has reviewed Comey's notes said the documents are dated and detailed, including the account of his Feb. 14 encounter with Trump where the president reportedly urged Comey to back off its examination of Flynn. The former national security adviser had been fired the day before for lying about his communications with Russia ambassador Sergey Kislyak before the inauguration.

"I hope you can let this go,'' Trump allegedly told Comey in the private meeting. The FBI director was at the White House that day for a broader national security meeting, which included Vice President Mike Pence and Attorney General Jeff Sessions. Following that gathering, Trump asked Comey to remain for a one-on-one discussion where Comey alleged Flynn's status was raised.

Comey felt it necessary to keep contemporaneous notes of all his meetings and telephone calls with the president because he regarded Trump with particular suspicion, according to a person who has reviewed the former director's memos. The existence of the memos was first reported by The New York Times.

It is not clear how widely the documents were circulated within the bureau.

Now that he's been fired, of course, the calculation to keep them under close hold might change: Trump has yet to appoint a new FBI director, and already questions are swirling as to whether that person will be able to take on the ongoing inquiry without bias.

In the days after firing Comey, Trump called Russia investigation a "made up story" and said in an interview to NBC that it was indeed on his mind when he fired the FBI chief. That contradicted his administration's assertions and even his own widely disseminated termination letter stating the dismissal was based on the recommendations of Justice Department leadership, who objected to his handling of the Hillary Clinton email probe.

Adding insult to injury, Trump called Comey – who only got the news he was fired through TV news reports at the Los Angeles bureau – a "showboat" and "grandstander" who led the agency into turmoil.

While Comey's management of the Clinton email investigation was strongly criticized by members of both parties during the election, few have questioned his personal integrity.

A career prosecutor, Comey held top Justice Department posts in the George W. Bush administration before being appointed FBI director by President Obama in 2013.

Comey has been widely lauded for his actions as deputy attorney general in the George W. Bush administration when he led a dramatic intervention in the hospital room of an ailing Attorney General John Ashcroft. Then-White House counsel Alberto Gonzales and chief of staff Andrew Card were pressing Ashcroft to renew a controversial warrantless wiretap program. When Comey and then-FBI director Robert Mueller threatened to resign, the White House relented.

With this kind of reputation as an independent straight shooter, it's likely members of Congress on both sides will take his accounts very seriously. Contemporaneous notes of events recorded by agents and investigators are often given strong consideration by courts, but it is not immediately known whether Comey specifically prepared them for use in the bureau's counter-intelligence inquiry involving Russia's election interference.

Trump's credibility also could take a hit from memos detailing Comey's controversial Jan. 27 dinner with the Trump, according to the person who has reviewed them.

The president claimed in an NBC News interview last week that Comey requested the dinner as part of an appeal to keep his job as FBI director. Trump also claimed that during the course of the dinner, Comey assured him that he was not a target of the bureau's ongoing Russia probe.

After skeptics of that account suggested that would have been highly unusual, or even inappropriate, for a director to give private assurances about the scope of an investigation, Trump later warned Comey against going public with any contradiction of the president's version of events, suggesting on Twitter that there were secret "tapes" of the encounter. The White House has refused to confirm or deny whether the president secretly records conversations.

But Comey's notes from that dinner meeting, according to the source familiar with them, do reflect that the president requested the FBI director's loyalty. The source said Comey pledged only honesty – and did not address Trump's status as a possible subject of the bureau's Russia investigation.

The White House has strongly disputed Comey's version of events, especially the memo involving Flynn.

"While the president has repeatedly expressed his view that General Flynn is a decent man who served and protected our country, the president has never asked Mr. Comey or anyone else to end any investigation, including any investigation involving General Flynn," the White House said in a statement.

"The president has the utmost respect for our law enforcement agencies, and all investigations," the White House said. "This is not a truthful or accurate portrayal of the conversation between the president and Mr. Comey.”

Former Trump campaign aide Michael Caputo said the true opponent isn't actually Comey – but the so-called "Never Trump" political faction establishment using the alleged memo as an excuse to attack the president. "It's not Comey who's flooding the zone, it is the anti-Trump zealots who are flooding the zone," Caputo said. "It's a shame they're making Comey a pawn in their play."

If the FBI truly believed Trump was attempting to interfere inappropriately with the Russia investigation, Caputo said Comey should have made his concerns known about the Flynn conversation.

"If Comey did not report it up the chain of command, it means he did not think it was obstruction of justice," Caputo said. "If he did, he would have been required by law to report it."

Caputo said Trump has faced crises before and prevailed, most notably in the November election. "I think Donald Trump is in for the fight of his life," he said, "and I think he's up for it."

The Justice Department, meanwhile declined comment Wednesday on either lawmakers' new requests for memos or the accusations Trump interfered with the probe. Deputy Attorney General Rod Rosenstein is preparing for a Thursday briefing for the full Senate to outline last week's decision to dismiss the FBI director.

Rosenstein, just two weeks on the job, prepared the scathing three-page letter offering justification for Comey's dismissal. The deputy attorney general specifically cited Comey's controversial management of the FBI's inquiry into Hillary Clinton's use of a private email server while secretary of State — in which he publicly declared that the agency would not seek charges against the Democratic candidate in July, only to announce the reopening of the probe just 11 days before the November election.

Trump later said he intended to fire Comey regardless of Rosenstein's recommendation. Still, the new disclosures about Comey's deep suspicion of Trump's motives are casting a sharper focus on the Justice Department leader's anticipated Senate appearance.

"Indeed, all of the circumstances surrounding Director Comey’s dismissal just as he was leading an investigation into ... the Trump campaign’s ties with Russia and President Putin’s interference with the 2016 election, have shaken public confidence in the (Justice) department, in your leadership, and in the administration of law and justice in our country,” Senate Minority Leader Chuck Schumer, D-N.Y., said in a letter to Rosenstein.

“In order to restore the nation’s faith in you personally and in our law enforcement system more broadly, the American people must understand more about your role in the president’s firing of Director Comey.”

Meanwhile, on Wednesday, with the news of notes now out in the open, Trump broke with his usual practice — and stayed quiet.

He did not tweet about the Comey memos in the 18 hours after news reports broke. And he steered clear of the topic at his commencement address at the U.S. Coast Guard Academy.

He did, however, insist that "no politician in history" has been "treated worse or more unfairly" than he has.

Even as he blasted the media coverage, and threats from his critics, Trump struck a defiant tone. "You can't let them get you down," Trump told the cadets. "Adversity makes you stronger. Don't give in, don't back down."