Look here, tyranny was discovered very early in human history, and identified very early as inimical to political life. Still, it has never in any way prevented any tyrant from becoming a tyrant. It did not prevent Nero, and it did not prevent Caligula. And the cases of Nero and Caligula have not prevented a much nearer example of what the massive intrusion of criminality into political processes means for human life.

Hannah Arendt (1906–1975) German-American philosopher, political theorist

Interview (1973-10) with Roger Errera, Office de Radiodiffusion-Télévision Française (ORTF)
    (Source)

Speaking (most proximately) about the Watergate scandal.

The interview was edited and retranslated in 2013 [tr. Andrew Brown], and collected in Arendt, Thinking without a Bannister: Essays in Understanding, 1953-1975 (2018) [ed. Jerome Kohn]. That is the text quoted.

Parts of this interview were turned into an episode of the French TV series "Un certain regard," directed by Jean-Claude Lubtchansky, first broadcast 1974-07-06. This portion of the interview comes at 49:17, and reads:

You see, tyranny has been discovered very early, and very early really as an enemy. Still, it has never in any way prevented any tyrant from becoming a tyrant. It has not prevented Nero, and has not prevented Caligula. And Nero and Caligula have not prevented a more closer example of what the massive intrusion of criminality can mean for the political process.