There's a scene in The Godfather Part II where Michael Corleone, the mobster played by Al Pacino, seems finally to have run out of luck: A Senate committee investigating corruption has him dead in their sights and has promised to introduce a witness to the public who can testify to Michael's crimes. Our anti-hero is finally going to pay for his sins.

Only the witness clams up.

It's not what anybody expected — least of all the committee chairman: "I'm gonna find out what the hell happened here," he growls. "Alright this committee is now adjourned. The witness is excused."

And Michael is free to go. We know he's a mobster. He knows he's a mobster. Everybody who has been watching the Senate hearings know it's almost certain he's a mobster. But they can't prove it. And so his lawyer, Tom Hagen, decides to press the advantage.

"Senator. Senator! This committee owes an apology!" Hagen shouts, as the scene comes to a close. "This committee owes an apology — apology, senator!"

Fade to black.

If you're guessing this anecdote is another movie mafia-themed metaphor for the Trump presidency, well, you're right. It is and should be obvious that Donald Trump is not a good president, much less an honest one. He looks, walks, and quacks like the most corrupt of ducks. But he has escaped the wrath of Special Counsel Robert Mueller — barely, where the question of corruption of justice is concerned — and so Trump's partisans will assure us that he is an innocent man with clean hands.

But Trump is not owed an apology.

He is not owed an apology, because — even if Mueller didn't turn up sufficient evidence to warrant an indictment — the question of links between Trump and Russia was entirely legitimate to investigate. Trump stood before the media in July 2016 and asked Russia to intervene in the election. Russia did intervene in the election. And Trump's behavior afterwards — his unwillingness to acknowledge Russia's help, his supine behavior when standing next to Vladimir Putin — was fishy. Under such circumstances, an inquiry was all but required. Even without an inquiry, the public has enough evidence to conclude that Trump acted badly, and that his election, if not illegitimate, was at least tainted.

He is not owed an apology because his own public behavior was thuggish. He fired Jim Comey, put the screws to Jeff Sessions, and has made it abundantly clear over the last two years that he expects the machinery of the U.S. government to serve him personally.

And let's be churlish here: Trump is not owed an apology because he would never give one. He spent years promoting his political prospects by spreading the "birther" lie that President Barack Obama was born in Kenya, then tried to take credit for the "truth" of Obama's citizenship being proved. His whole career is built on the idea that an apology — no matter his behavior, no matter how warranted — shows weakness. Let him live by the rules he applies to others.

Despite the frustrations of this moment — we can see how awful Trump is, so why didn't Mueller make a stronger case? — I am sticking with my initial assessment of this affair: I still believe that Robert Mueller has been an exemplary public servant in handling the Trump investigation. What now seems obvious is that he was also extremely cautious: He left the question of obstruction of justice to his bosses at the Department of Justice. That's a sign he believed a great deal of circumspection is required before making criminal allegations against the president of the United States and thus potentially undoing the results of an election. If that decision was going to be made, and if it was a close call — Mueller apparently thought so — then it had to be made at a higher pay grade.

That's appropriate, actually.

Going forward, it remains imperative that Attorney General William Barr release the entire report to the public. There's a difference between being able to establish evidence of a crime and full exoneration, and the cautious wording of Barr's letter on Sunday suggests that Mueller's findings fall into the former category. The American public deserves to see what is known.

And we should remember that other investigations are outstanding. There are criminal and civil inquiries going on at the state and federal level, into his business, his charitable foundation, and into other activities. Congress has its own lines of inquiry to pursue, and they should be pursued with vigor.

This is not a great moment for Trump's critics. We can see that he is a bad president and to watch his defenders proclaim him exonerated is frustrating and troubling. The work to hold this president accountable for his behavior isn't ending, though. Someday — sooner or later — the truth will at long last catch up to Trump. That too might be a painful moment. In the meantime, those who pursue that truth should keep working — and never apologize.