It's attributed to Edmund BURKE!
"Here is where you would expect that famous quote from Edmund Burke. Something like ‘All that’s necessary for the forces of evil to win in the world is for enough good men to do nothing.’ Not sure of the exact quote, I looked it up. Here’s what I found: ‘When bad men combine, the good must associate; else they will fall one by one, an unpitied sacrifice in a contemptible struggle.*’ Not quite the same thing, but easy to understand the transformation, a good quote made better by its passing into common wisdom." . . .
The quote you seek is generally attributed to Edmund Burke, an 18th
Century British Statesman, famous for impeaching Warren Hastings, book on the French Revolution ("Reflections on the Revolution In France") and some fairly liberal positions towards the American colonies. To my knowledge, no one has ever *found* the quote in any of his writings, and it remains more elusive than 1943 copper pennies. Your form is close enough, given that the original has never been found; however, I’ve usually seen it more in the form of "All that is necessary for the forces of evil to succeed/triumph is for enough good men to do nothing." Frank Lynch"
http://72.14.207.104/search?q=cache:6iAN0-SQTS0J:www.tartarus.org/~martin/essays/burkequote2.html+tyranny+remain+silent&hl=en ***********
dunno who started the Jefferson rumour......