WASHINGTON – Surrounded by multiplying questions, President Donald Trump complained Wednesday that “no politician in history” has been treated worse. Democrats demanded an independent commission to dig into his firing of FBI Director James Comey, but Republican House Speaker Paul Ryan cautioned against “rushing to judgment.”

Ryan said Congress needs to get the facts, but “it is obvious there are some people out there who want to harm the president.” Elijah Cummings, top Democrat on a key House oversight panel, countered that Ryan and the Republicans had shown “zero, zero, zero appetite for any investigation of President Trump.”

The White House has denied reports that Trump pressed Comey to drop an investigation into Trump’s first national security adviser, Michael Flynn. In addition Trump is facing pointed questions about his discussions with Russian diplomats during which he is reported to have disclosed classified information.

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Also Tuesday, in an extraordinary turn of events, Russian President Vladimir Putin offered to turn over to Congress records of Trump’s discussions with the diplomats.

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The White House has played down the importance and secrecy of the information Trump gave to the Russians, which had been supplied by Israel under an intelligence-sharing agreement. Trump himself said he had “an absolute right” as president to share “facts pertaining to terrorism” and airline safety with Russia. Yet U.S. allies and some members of Congress have expressed alarm.

Republicans and Democrats alike were eager to hear from Comey, who has increasingly emerged as a central figure in the unfolding drama.

The Senate intelligence committee on Wednesday asked Comey to appear before the panel in both open and closed sessions. The committee also asked acting FBI Director Andrew McCabe to give the committee any notes that Comey might have made regarding discussions he had with White House or Justice Department officials about Russia’s efforts to influence the 2016 presidential election.

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WATCH: Report claims President Trump asked former FBI director James Comey to end investigation into Michael Flynn.

1:39 Trump asked ex-FBI director James Comey to stop investigating Flynn’s Russia ties: reports Trump asked ex-FBI director James Comey to stop investigating Flynn’s Russia ties: reports

Putin told a news conference that he would be willing to turn over notes of Trump’s meeting with the Russian diplomats if the White House agreed. He dismissed outrage over Trump’s disclosures as U.S. politicians whipping up “anti-Russian sentiment.”

Asked what he thinks of the Trump presidency, Putin said it’s up to the American people to judge and his performance can be rated “only when he’s allowed to work at full capacity,” implying that someone is hampering Trump’s efforts.

Trump himself hasn’t directly addressed the latest allegations that he pressured Comey to drop the Flynn investigation. But the swirling questions about his conduct were clearly on his mind when he told graduates at the U.S. Coast Guard Academy in Connecticut that “no politician in history, and I say this with great surety, has been treated worse or more unfairly.”

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Striking a defiant stance, he added: “You can’t let the critics and the naysayers get in the way of your dreams. … I guess that’s why we won. Adversity makes you stronger. Don’t give in, don’t back down. … And the more righteous your fight, the more opposition that you will face.”

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As for Comey, whom Trump fired last week, the FBI director wrote in a memo after a February meeting at the White House that the new president had asked him to shut down the FBI’s investigation of Flynn and his Russian contacts, said a person who had read the memo. The Flynn investigation was part of a broader probe into Russian interference in last year’s presidential election.

Comey’s memo, an apparent effort to create a paper trail of his contacts with the White House, would be the clearest evidence to date that the president has tried to influence the investigation.

Rep. Jason Chaffetz, Republican chairman of the House oversight committee, sent a letter to the FBI on Tuesday requesting that it turn over all documents and recordings that detail communications between Comey and Trump. He said he would give the FBI a week and then “if we need a subpoena, we’ll do it.”

Rep. Jason Chaffetz said in a tweet Wednesday that he still hasn’t spoken with Comey about testifying. But he has set a hearing for May 24.

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Officially noticed a hearing for next Wed at 9:30am ET with former FBI Dir Comey. But I still need to speak with him…evidently has a new # — Jason Chaffetz (@jasoninthehouse) May 17, 2017

The moves comes a day after it was disclosed that Comey had written a memo detailing how Trump had asked him to shut down the investigation into Flynn. The FBI has been looking into Flynn for months as part of a counterintelligence investigation.

Chaffetz has demanded that the FBI turn over Comey’s memos. He says he wants to determine whether the president attempted to influence or impede the FBI’s investigation into Flynn.

John McCain, chairman of the Senate Armed Services Committee, said late Tuesday that the developments had reached “Watergate size and scale.”

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2:22 Donald Trump talks about his upcoming trip abroad, his first as president Donald Trump talks about his upcoming trip abroad, his first as president

Mitch McConnell, the Republican leader of the Senate, said simply, “It would be helpful to have less drama emanating from the White House.”

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The person who described the Comey memo to the AP was not authorized to discuss it by name and spoke on condition of anonymity. The existence of the memo was first reported Tuesday by The New York Times.

The White House vigorously denied it all. “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,” a White House statement said.

Trump fired Flynn on Feb. 13, on grounds that he had misled Vice-President Mike Pence and other officials about his contacts with Russians.

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The intensifying drama comes as Trump is set to embark Friday on his first foreign trip, which had been optimistically viewed by some aides as an opportunity to reset an administration floundering under an inexperienced president.

Mark Warner of Virginia, top Democrat on the Senate intelligence committee, said he would ask Comey for additional material as part of that panel’s investigation. “Memos, transcripts, tapes – the list keeps getting longer,” he said.

According to the Times, Comey wrote in the February memo that Trump told him Flynn had done nothing wrong. Comey said he replied that “I agree he is a good guy” but said nothing to Trump about limiting the investigation.

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Associated Press writers Vivian Salama and Jill Colvin contributed.