https://www.salon.com/2021/08/29/joe-mccarthy-was-never-defeated--and-donald-trump-now-leads-the-movement-he-created/
McCarthy was rewarded with a powerful chairmanship, at the Senate Committee on Government Operations, where Cohn and the young Robert F. Kennedy serving as assistant counsels. There he targeted the Voice of America, the overseas library program of the International Information Agency (this led to book burnings), several prominent Protestant clergymen and finally the U.S. Army. That last crusade proved to be a bridge too far: Joseph Welch, chief counsel for the Army, called out McCarthy on national television for his cruelty and recklessness, famously demanding, "At long last, sir, have you no decency?"
For author Sam Roberts, the essence of Cohn's influence on Trump was the triad: "Roy was a master of situational immorality . ... He worked with a three-dimensional strategy, which was: 1. Never settle, never surrender. 2. Counter-attack, counter-sue immediately. 3. No matter what happens, no matter how deeply into the muck you get, claim victory and never admit defeat." As columnist Liz Smith once observed, "Donald lost his moral compass when he made an alliance with Roy Cohn."