Roy Cohn, who slithered his way through 20th-century American history, had the worst friends.

Senator Joseph McCarthy, who brought the fire and the stake to America’s latter-day Salem Witch Trials during the 1950s, was chief among them. The lawyer was pals with the notorious gossip columnist Walter Winchell, a one-man lynch mob of the media, who enjoyed enormous influence until he didn’t. In his dotage, Cohn also befriended another deeply damaged power seeker, Donald Trump, sharing with the then-young builder his lifetime learning of the dark arts of character assassination and skullduggery. The lessons stuck.

In a Guardian article, Michelle Dean recalls the latter union, an unholy one by any measure. The opening:

Donald Trump is a man who likes to think he has few equals. But once upon a time, he had a mentor: Roy Cohn, a notoriously harsh lawyer who rose to prominence in the mid-1950s alongside the communist-baiting senator Joseph McCarthy. His tactics would often land him in the papers, but Cohn was unafraid of being slimed by the press – he used it to his advantage. A devil-may-care-as-long-as-it-gets-a-headline attitude was Cohn’s trademark in life. Trump, in our time, has made it his.

His careful manipulation of negative attention is something that Trump noticed immediately when the two met in 1973. Trump and his father had just been sued for allegedly discriminating against black people in Trump’s built-and-managed houses in Brooklyn, and sought out Cohn’s counsel. Among other things, Cohn advised that Trump should “tell them to go to hell”. Cohn was hired, and one of his first acts as Trump’s new lawyer was to file a $100m countersuit that was quickly dismissed by the court. But it made the papers.

This was the beginning of a long and close relationship. Trump relied on Cohn for most of the legal matters during a particularly tricky decade. Cohn drew up the pre-nuptial contract between Donald and Ivana when they married in 1977 – a famously stingy contract that only gave Ivana $20,000 a year. Cohn also filed a suit brought by the United States Football League in 1984 against the NFL, seeking to break up the monopoly held over American football. Trump owned a USFL team and was widely seen as the force behind the suit; the initial press conference about it was a tag-team show performed by Cohn and Trump.

“I don’t kid myself about Roy. He was no Boy Scout. He once told me that he’d spent more than two-thirds of his adult life under indictment on one charge or another. That amazed me,” Trump wrote in The Art of the Deal. The unabashed pursuit of power, quick resort to threats, a love of being in the tabloid spotlight – all of these are things Trump took from his mentor.

In fact, if you’re familiar with Cohn’s history at all, their friendship starts to seem an even greater influence on Trump than any other.•