WASHINGTON (AP) — For three hours, former FBI Director James Comey leveled an unrelenting attack on the credibility of the president of the United States.

The White House's statements were "lies, plain and simple." Comey took notes on their conversations because he worried the president "might lie" later. After a while, he said, he so distrusted the man running the country that he did not want to be left alone with him.

It was a riveting, televised portrait of President Donald Trump, one unrivaled in recent memory for its potential to undermine a presidency. Comey's message, delivered in meticulous detail, amounted to a challenge to lawmakers, the public and the special counsel now investigating possible links between Trump's campaign and Russia: Whose account do you believe — the nation's former top law enforcement official testifying under oath or a president with a record of skirting the truth on issues big and small?

The answer to that question ultimately may not impact the outcome of the FBI and congressional Russia probes, and it may not move Republican lawmakers any closer to a dramatic break from their party leader. But it could leave the president in a perilously weak political position not yet five months into his term.

"A president cannot communicate effectively if their trust tank is full of holes and credibility has leaked out all over the political landscape," said Matthew Dowd, who served as chief strategist for President George W. Bush's re-election campaign.

A Gallup poll conducted in April found that just 36 percent of Americans found Trump "honest and trustworthy" — down from 42 percent in February.

The White House and the president's personal lawyer vigorously vouched for Trump's integrity, saying he did not try to get the FBI to end the Michael Flynn investigation and also did not seek a loyalty pledge from Comey. Both were quick to note that Comey validated one Trump claim: that Comey had told him three times that he was not personally the target of the investigation.

"I can definitively say the president is not a liar, and I think it's frankly insulting that question would be asked," spokeswoman Sarah Huckabee Sanders said.

Comey himself is a controversial figure. He outraged Democrats last year with his handling of the investigation into Hillary Clinton's email practices, including the decision to publicly disclose the potential of new information 10 days before the election. During his final appearance on Capitol Hill as FBI director, he vastly overstated the number of emails that were uncovered late in the campaign, prompting the bureau to correct his testimony.

Still, it was telling that few Republicans who don't work for Trump stepped in to defend the president's version of his contacts with the former FBI director. The toughest questioning of Comey by GOP lawmakers on the Senate intelligence committee focused more on whether the interactions he described amounted to legal trouble for Trump than on whether he was telling the truth about the nine meetings and phone calls he had with the president.

Instead, some supportive GOP lawmakers simply argued that Trump's action were a result of well-meaning inexperience or dedication to his aides.

"I'm frankly proud of him for standing up for someone who was as loyal as Mike Flynn was throughout the campaign," Rep. Chris Collins, R-N.Y., said of Comey's dramatic depiction of an Oval Office meeting in which Trump allegedly said he hoped the FBI would let the Flynn investigation go. Collins spoke after the prepared text of Comey's opening statement was released Wednesday.

House Speaker Paul Ryan also did not dispute Comey's assertions. He vouched for the importance of the FBI's independence, and excused Trump's blurring of that line as missteps by a man who isn't "steeped in the long-running protocols" that govern the relationship between the White House and the law enforcement agency.

"The president's new at this. He's new at government," Ryan told reporters on Capitol Hill as Comey's dramatic testimony unfolded. "He's learning as he goes."

Yet Trump's own track record — as president, a candidate and private citizen — make the questions about the veracity of his own words impossible for the White House to avoid. He memorialized his approach to accuracy in his 1987 book "The Art of the Deal," writing: "People want to believe that something is the biggest and the greatest and the most spectacular. I call it truthful hyperbole."

Trump's shift from real estate mogul and reality TV star to political powerhouse was driven in part by his campaign to spread the lie that President Barack Obama was born outside the United States. He spent his first full day occupying the world's most powerful office inflating the size of the inaugural crowd and demanding that his advisers do the same. Last month, he created a voter fraud commission to investigate "millions of people who voted illegally," despite there being no proof of such fraudulent voting.

The president's abrupt firing of Comey on May 9 — and the White House's bungled handling of the controversial move — has intensified questions about Trump's credibility. At first, the White House cited a harsh memo about Comey's performance from Deputy Attorney General Rod Rosenstein as the justification, though Trump later said he would have fired Comey regardless of what the Justice Department recommended.

When Comey allies began fighting back with negative stories about Trump in the press, the president issued a startling warning on Twitter: "James Comey better hope that there are no 'tapes' of our conversations before he starts leaking to the press!"

The White House has avoided all questions about whether such tapes exist. But Comey confidently asserted that if there are recordings, they will back up his testimony.

"Lordy, I hope there are tapes," Comey said.

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EDITOR'S NOTE — Julie Pace has covered the White House and politics for The Associated Press since 2007. Follow her at http://twitter.com/jpaceDC

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Associated Press writer Jill Colvin contributed to this report.