In a recent tweet, President Donald Trump charged that President Obama had wiretapped his calls in Trump Tower during the election campaign. “This is McCarthyism!” he exclaimed.

That allegation is rich in irony since Trump himself is sometimes compared these days to Senator Joseph McCarthy, the notorious political demagogue of the ’50s. Indeed, there is a direct connection between McCarthy and Trump in the person of Roy Cohn, who was chief counsel to McCarthy’s permanent investigations subcommittee in 1953-54.

Twenty years later, when Trump and his father were sued by the Justice Department for discriminating against black tenants in their housing developments, Cohn advised them, “Tell them to go to hell and fight the thing in court.” They did and eventually settled.