Did Einstein say, 'Insanity is doing the same thing over and over again and expecting different results'?

Online users have for years — "over and over again" — shared the quote with the famous physicist's name and image.
The Salt Lake Tribune

Letter: It is simply insanity to continue to pursue the mirage of “trickle-down” economics. The data is clear.

What is the definition of insanity? A popular quote — attributed to Albert Einstein but most likely from author Rita Mae Brown (novel “Sudden Death” published in 1983; character of Jane Fulton) — ...