In a Parliamentary debate with the Conservative MP, John Pakington (May 31, 1866). Hansard, vol 183, col 1592. Pakington was referring to Footnote 3 to Chapter 7 of Mill's "Considerations on Representative Government".
Misquoted as "I never meant to say that the Conservatives are generally stupid. I meant to say that stupid people are generally Conservative. I believe that is so obviously and universally admitted a principle that I hardly think any gentleman will deny it." in "Life of John Stuart Mill" (1889) by W. L. Courtney, p. 147.
This seems to have become paraphrased as "Conservatives are not necessarily stupid, but most stupid people are conservatives." which was a variant published in Quotations for Our Time (1978), edited by Laurence J. Peter.
