THE NEWS this week emerged in such fits and starts, and with such shifting explanations, that its grave implications may not have sunk in for many Americans. It is worth reviewing what we know:

(1) President Trump fired the director of the FBI, in the fourth year of his 10-year term, because the president was upset that Mr. Comey was leading an FBI investigation of possible collusion between Russia and the Trump campaign in 2016. The investigation was gaining momentum as Mr. Trump struck.

(2) Mr. Trump initially misrepresented the reason for the firing and allowed other members of his administration, including Vice President Pence, to grossly misinform Congress and the public. Mr. Trump’s initial letter gave the impression that he was acting on a recommendation from the Justice Department and that Mr. Comey was fired for mishandling the investigation of Hillary Clinton’s emails. “It was all him,” spokesman Sean Spicer said, referring to Deputy Attorney General Rod J. Rosenstein. “That was a DOJ [Department of Justice] decision,” he said. Mr. Pence portrayed Mr. Rosenstein as initiating the action — he “came to work, sat down and made the recommendation” — and Mr. Trump as simply “accepting” it.

By Thursday, in his interview with NBC’s Lester Holt, Mr. Trump was acknowledging that he decided to fire Mr. Comey before soliciting and receiving any recommendations and that the Clinton emails were not his motivation. “When I decided to just do it, I said to myself, I said, you know, this Russia thing with Trump and Russia is a made-up story.”

(3) In January, according to Mr. Trump, the president dined privately with Mr. Comey at Mr. Comey’s request and asked the FBI director to tell him whether he was under investigation. That would be troubling. In a more troubling — and, in our view, more plausible — version provided by Mr. Comey’s associates, the president initiated the dinner and used the occasion to demand the FBI director’s “loyalty.”

(4) On Friday, as the contradictory versions of that dinner added to Mr. Trump’s political difficulties, he issued a menacing tweet — “James Comey better hope that there are no ‘tapes’ of our conversations before he starts leaking to the press!” — and threatened to cancel the daily press briefings through which presidents normally communicate their plans and policies to the American people.

Some of what we learned from this series of events is only a matter of relearning. Mr. Trump’s inconstant fidelity to truth, for one example: Just think back to the thousands of Muslims he claimed to see celebrating the 9/11 attacks. His breezy contempt for the rule of law, for another: Recall his attacks on Judge Gonzalo P. Curiel during the campaign and on the “so-called” judge who blocked his visa ban. His personalization of every issue is hardly news either.

But this week he wielded these traits in a manner that threatened the independence of federal law enforcement and sullied key institutions of U.S. democracy. The White House Counsel’s Office, which is meant to defend the presidency and not just the president, failed to rise to the occasion. A half-dozen administration officials knowingly or unwittingly spoke falsehoods. The attorney general arguably violated his pledge to recuse himself from all matters related to Russia and the election, and the newly installed deputy attorney general found himself compromised. The president injected himself into an investigation where he has absolutely no right to interfere.

We have said for months that that investigation — into Russian meddling in the U.S. election — must be a priority for both the executive and legislative branches. We need to know what the Russians did and take steps to prevent a recurrence. To that urgent inquiry now must be added an investigation into the events and disclosures of this week. Congress and the American people must hear from Mr. Comey and Mr. Rosenstein, and Congress must ensure that the Russia investigations proceed, unfettered.