When the snowball was first forming on the ever-swelling avalanche that began as “The Trump/Russia Investigation,” the increasingly embattled 45th president was quoted making this plea from inside the White House.

“Where’s My Roy Cohn?”

He was elected, apparently with massive foreign intervention, by millions of Americans who should have remembered that name and been instinctively repulsed by Donald Trump’s “protege” association with the most dishonest, corrupt and repellant figure in American politics, “America’s Machiavelli,” a man whose evil took on Bond villain proportions.

The name “Roy Cohn” inspired fear and revulsion during his lifetime, and provided the perfect self-loathing monster in the epoch-defining Broadway show “Angels in America.” He was that infamous.

But here’s a documentary for the millions who didn’t get the name or the association. Documentarian Matt Tyrnauer (“Studio 54,” “Valentino: The Last Emperor”) finds another gay subject to profile in this portrait of a man whose very proximity let you know, one witness in the film declares, “you were in the presence of evil.”

Tyrnauer’s thorough rummage through Roy M. Cohn’s life and the damage he left in his wake is built on interviews he did from an early age. He was a high profile Justice Department lawyer interviewed on an ocean liner in 1951, at age 23. He’s seen bantering on chat shows over the decades, swapping shots with novelist and wit Gore Vidal (who was ONTO him, and witheringly so) all the way to his bitter — and one cannot stress that word enough, BITTER — end-of-life chat with Larry King.

The cornerstone interview featured here is with journalist Ken Auletta, whose 1970s Esquire Magazine profile of Cohn the reporter recorded. The tapes capture Cohn’s dissembling, counter-attacking style, a man described by family as a classic “self-hating Jew” who only gets rattled when Auletta brings up the open secret of Cohn’s life — that he was also a self-loathing homosexual.

“Where’s my Roy Cohn?” traces Cohn’s birth, into a wealthy family whose father was essentially bribed to marry “the ugliest girl in the Bronx.” An only child and a homely one whose parents never let him forget that, he carried secret and not-so-secret shames and a very public chip on his shoulder out of that wealth and into the walls of power.

A relative relates how he committed his first bribe at 15, finished law school too young to yet take the bar, learned how to bully from his corrupt family and how to play the demagogue once he hooked up with Senator Joseph McCarthy, whose media-grabbing lies, tirades and attacks gave a name to an entire era.

There is history here that even those who remember Cohn and his lying, thieving, mob-connected legacy (he was finally disbarred late in life) might have forgotten. Cohn’s first public work was his involvement in the Rosenberg spy case, and he took credit for getting (in phone calls he claims he had with the judge) atomic-secret stealing Julius and Ethel Rosenberg the electric chair. Tyrnauer’s witnesses suggest Cohn and Judge Irving Kaufman, both Jewish like the Rosenbergs, pushed for execution to prove their own loyalty to America.

His time as McCarthy’s “handmaiden” — whispering in the senator’s ear during Senate hearings McCarthy lorded over — is recounted, as is the senator’s fall. The end of McCarthy and the tipping point of the entire McCarthy Era, which had succeeded in putting Eisenhower in the White House, came because of Cohn’s secret sexuality and his willingness to use power unscrupulously.

He tried to get a favor for a handsome colleague he had a crush on, a fellow McCarthy staffer who had just been drafted. The “Army-McCarthy Hearings” spun out of Cohn’s eagerness to deliver special treatment and placement of his “special friend,” G. David Schine.

We’re shown clips of hearings pierced with laughter about “pixies” and “fairies.”

Yes, it took nationally-televised gay bashing to end the amoral, self-destructive witch hunt of McCarthyism. Didn’t see that in “Good Night, and Good Luck,” did you?

As a person and as a lawyer, he “never played by the rule book,” one and all agree. There was his underhanded way of taking over the extended family’s most famous property, the Lionel Trains toy company (“which he ran into the ground”), the mysterious fire that sank his heavily-insured motor yacht “Defiance” and killed a young crewman, and the death’s door-bedside visit with a “client” wangling a signature that made him executor of an estate, the final straw crime in a career littered with them that led to his disbarment and undoing.

“Amoral” is one of those words, like “cutthroat” and “ruthless,” that Cohn relished having attached to his name. And the implication is, these are all ways of lying, living and operating that he passed on to his star protege and sometime client, Donald J. Trump.

Cultivate the press with gossip and favors, “wrap yourself in the flag.” “Never apologize, never admit defeat, or that you’ve lost, never leave a paper trail,” don’t be shy about endlessly repeating the same lies, always “attack” so that you control what the conversation is about (changing the subject), avoid taxes to the point where you “die owing the IRS a fortune,” and if “they’re on to you,” “rat out other people.”

Sound familiar? In the month since this documentary went into limited release, it’s proven prophetic about events as crimes are alleged or revealed in Washington. “Where’s My Roy Cohn?” even seems to predict how the tidal wave of high crimes and misdemeanors might play out.

The end game for Roy M. Cohn, who died in 1986, makes it all seem too familiar.

MPAA Rating:PG-13 for thematic content, some sexual material and violent images

Cast: Roy Cohn, Ken Auletta, Liz Smith, Gore Vidal, Larry King, etc.

Credits: Directed by Matt Tyrnauer. A Sony Pictures Classics release.

Running time: 1:37