There have been three memorable American presidents, the story goes. President George Washington could never tell a lie. President Richard Nixon could never tell the truth. And President Donald Trump cannot tell the difference. At a White House news conference, Trump referred to his November 2016 victory, in which he received 304 electoral votes, as “the biggest Electoral College win since Ronald Reagan,” who was re-elected in 1984. Wrong. After Reagan and before Trump, Presidents George H.W. Bush, Bill Clinton and Barack Obama each won many more electoral votes than did Trump. When NBC’s Peter Alexander pointed out Trump’s misstatement to him, the president responded: “I don’t know. I was given that information. Actually, I’ve seen that information around.”

The changing explanations for President Trump’s firing of FBI Director James Comey — in a way calculated to publicly and personally humiliate the director through his learning about his termination over cable TV news while he was in Los Angeles thanking FBI employees — remind us again of the president’s only intermittent flirtations with candor.

The earnest and nonthreatening vice president, Mike Pence, assured the nation: “Let me be very clear that the president’s decision to accept the recommendation of the deputy attorney general (Rod Rosenstein, in case you forgot) and the attorney general to remove Director Comey … was based solely and exclusively on his commitment to the best interest of the American people and to ensuring that the FBI has the trust and confidence of the people of this nation.” In less measured prose, this had also been the rationale for the president’s sacking of Comey offered by a succession of White House spokespeople.

Pence might want to first check the most recent Wall Street Journal/NBC News poll, which asked voters their positive or negative feelings toward a number of well-known individuals and institutions. Pence’s favorite House speaker, Paul Ryan, was low man. Ryan’s negative score was 18 percentage points higher than his positive score. The Republican Party’s negative score was 16 points higher. And Trump himself had a negative score that was 11 points higher than his positive score. Justice Neil Gorsuch, the National Rifle Association, Obama and Planned Parenthood all received net positive scores. But at the top of the list, with a net positive-over-negative rating of 29 percentage points, was the “beleaguered” Federal Bureau of Investigation.

The official White House-VP explanations were exposed as untrue. Deputy Attorney General Rosenstein complained to White House counsel Don McGahn, insisting that the White House-Pence statements were misleading and wrong. Rosenstein claimed that Trump had on Monday asked him for his Tuesday letter on Comey’s performance and that Rosenstein had never explicitly called for Comey’s dismissal. But Rosenstein, a career federal prosecutor who was previously respected by both Democrats and Republicans, had been used to mislead the press and the public on why Comey was fired. Question: Can we think of one individual whose reputation for personal and professional integrity has not been sullied or diminished by that individual’s close identification with the Trump White House?

But never mind. President Trump told NBC News, “Regardless of (the deputy attorney general’s) recommendation, I was going to fire Comey.” He said Comey was guilty of being a “showboat” and a “grandstander.” Being called a showboat by the narcissist in the Oval Office is like being called ugly by a frog.

The credibility of and public confidence in this White House and its elected occupant are being depleted almost daily. Does Donald Trump have the courage or the self-confidence that President Gerald Ford did in October 1974 when he became the first U.S. president since Abraham Lincoln to voluntarily testify before Congress in defending his pardon of the disgraced Richard Nixon? For this presidency, time is short and the challenge is grave.

— Mark Shields is a columnist with Creators Syndicate.