Former F.B.I. officials took the report as vindication because it dispelled the many unfounded claims Mr. Trump and his supporters advanced about the bureau even as they fretted that too many people would still believe the president’s assertions. “There is a risk we’ve become so numb to the lying that we move onto the next outrage,” the former F.B.I. director James B. Comey, who was fired by Mr. Trump, said on CNN.

Likewise, the House Judiciary Committee impeachment hearing on Monday offered conflicting versions to suit either side’s predilections — either the story of an out-of-control president abusing his power to pressure a foreign government to help him take down his domestic rivals or a president who just happened to be concerned about corruption in faraway Ukraine and did not tie American aid to his political priorities even though some of his own advisers thought he did.

Mr. Trump’s insistence that he did nothing wrong has forced at least some Republicans to accept and promote his account even when it contrasts with available evidence. A Republican lawyer presenting the case to the committee on Monday went so far as to say that the evidence did not show that Mr. Trump asked Ukraine’s president to investigate former Vice President Joseph R. Biden Jr. during a now-famous July 25 phone call even though the White House’s own reconstructed transcript quoted him asking his counterpart to “look into it.”

Mr. Trump is hardly the first dissembler in the White House. Lyndon B. Johnson and Richard M. Nixon were famously talented liars, and Bill Clinton was the first president ever found by a court to have testified falsely under oath. But what Mr. Trump lacks in finesse, he makes up in volume. The Post’s fact-checking unit counted more than 13,000 false or misleading statements by Mr. Trump as of October.

The trials of truth have been a consistent theme of his presidency since its first day when he overstated his inaugural crowd size and within days falsely claimed that at least three million immigrants voted illegally against him, costing him the popular vote.

The culture of dishonesty has resulted in multiple people once in his inner circle pleading guilty or being convicted of lying to the authorities, including his onetime national security adviser, Michael T. Flynn; his former personal lawyer, Michael D. Cohen; several campaign aides; and most recently, his longtime associate and sometime adviser Roger J. Stone Jr., who was found guilty last month in a courthouse just across from the Capitol.

Mr. Trump’s former campaign manager, Corey Lewandowski, made clear during testimony before Congress in September that he felt perfectly free to lie on television because, in his view, the news media itself was dishonest. “I have no obligation to have a candid conversation with the media whatsoever, just like they have no obligation to cover me honestly, and they do it inaccurately all the time,” he told lawmakers.