The actor Jimmy Stewart played Jefferson Smith in the film Mr. Smith Goes to Washington (1939), saying these now-famous lines:
 
“I guess this is just another lost cause, Mr. Paine. All you people don’t know about lost causes. Mr. Paine does. He said once they were the only causes worth fighting for, and he fought for them once, for the only reason any man ever fights for them: Because of one plain simple rule: Love thy neighbor. And in this world today, full of hatred, a man who knows that one rule has a great trust. You know that rule, Mr. Paine. And I loved you for it just as my father did, and you know that you fight for the lost causes harder than for any others. Yes, you even die for them, like a man we both know, Mr. Paine. You think I’m licked. You all think I’m licked. Well, I’m not licked, and I’m gonna stay right here and fight for this lost cause, even if this room gets filled with lies like these!”
 
“Lost causes are the only ones worth fighting for” (or “Lost causes are the only causes worth fighting for”) is often credited to the lawyer Clarence Darrow (1857-1938), but there is no evidence that he ever said it.
 
The line dates to at least December 1903, when Blackwood’s Magazine published “Oxford Revisited”: “Oxford is reserved by a wholly beneficent fate to be the ‘home of lost causes,’ and she will never prove false to her destiny. For lost causes are the only causes worth fighting for, if they happen to be causes at all.” Matthew Arnold (1822-1888) had called the University of Oxford the “home of lost causes” in 1865.
   
The saying appeared in two books in 1936. Evelyn Wells wrote in Fremont Elder (1936): “It looks now as if you had cast your lot with a lost cause, but you and I know that lost causes are the only ones worth while.” Ethel Lina White wrote in The Wheel Spins (1936): “Lost causes are the only causes worth fighting for.”
   
It is unclear from what source Mr. Smith Goes to Washington screenwriter Sidney Buchman first heard the “lost cause” saying.
   
 
Wikipedia: Mr. Smith Goes to Washington
Mr. Smith Goes to Washington is a 1939 American drama film starring James Stewart and Jean Arthur, about one man’s effect on American politics. It was directed by Frank Capra and written by Sidney Buchman, based on Lewis R. Foster’s unpublished story. Mr. Smith Goes to Washington was controversial when it was released, but also successful at the box office, and made Stewart a major movie star. The film features a bevy of well-known supporting actors, among them Claude Rains, Edward Arnold, Guy Kibbee, Thomas Mitchell and Beulah Bondi.
 
Mr. Smith Goes to Washington was nominated for 11 Academy Awards, winning for Best Original Story. In 1989, the Library of Congress added the movie to the United States National Film Registry, for being “culturally, historically, or aesthetically significant.”
     
Wikiquote: Mr. Smith Goes to Washington
Mr. Smith Goes to Washington is a 1939 film about a naive and idealistic man who is appointed to fill a vacancy in the US Senate. His plans promptly collide with political corruption, but he doesn’t back down.
 
Directed by Frank Capra. Written by Sidney Buchman.
 
Jefferson Smith
[His voice very hoarse] I guess this is just another lost cause, Mr. Paine. All you people don’t know about lost causes. Mr. Paine does. He said once they were the only causes worth fighting for, and he fought for them once, for the only reason any man ever fights for them: Because of one plain simple rule: Love thy neighbor. And in this world today, full of hatred, a man who knows that one rule has a great trust. You know that rule, Mr. Paine. And I loved you for it just as my father did, and you know that you fight for the lost causes harder than for any others. Yes, you even die for them, like a man we both know, Mr. Paine. You think I’m licked. You all think I’m licked. Well, I’m not licked, and I’m gonna stay right here and fight for this lost cause, even if this room gets filled with lies like these! [takes a handful of the letters in the basket and throws them on the floor]. When the Taylors and all their armies come marching into this place, somebody’ll listen to me! So—- [Faints from exaustion]
 
Wikiquote: Clarence Darrow
Clarence Darrow (April 18, 1857 – March 13, 1938) was an American lawyer, best known for having defended teenaged thrill killers Leopold and Loeb in their trial for murdering 14 year old Bobby Franks (1924) and defending John T. Scopes in the so-called “Monkey” Trial (1925), opposing William Jennings Bryan.
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Misattributed
Lost causes are the only ones worth fighting for.
. This quote is from Ethel Lina White’s The Wheel Spins (1936). It was popularized in the film Mr. Smith Goes to Washington (1939). In this film a similar line was spoken by “Jefferson Smith” (Jimmy Stewart).
 
Wikiquote: Ethel Lina White
Ethel Lina White (1876 – 1944) was a British crime writer, best known for her novel, The Wheel Spins, on which the 1938 film, The Lady Vanishes was based.
 
Sourced
Lost causes are the only causes worth fighting for.
. The Wheel Spins (1932), p 270. (1936 is the correct date—ed.)
. A variation of this quote also appears in the film Mr. Smith Goes to Washington.
 
Wikiquote: Matthew Arnold
Matthew Arnold (1822-12-24 – 1888-04-15) was an English poet, essayist and cultural critic. He also pursued a career as an inspector of schools.
(...)
Essays in Criticism, first series (1865)
Whispering from her [Oxford’s] towers the last enchantments of the Middle Age…Home of lost causes, and forsaken beliefs, and unpopular names, and impossible loyalties!
. Preface
 
Google Books
December 1903, Blackwood’s Edinburgh Magazine, “Oxford Revisited,” pg. 765:
Oxford is reserved by a wholly beneficent fate to be the “home of lost causes,” and she will never prove false to her destiny. For lost causes are the only causes worth fighting for, if they happen to be causes at all.
 
Google Books
Fremont Older
By Evelyn Wells
New York, London, D. Appleton-Century Co.
1936
Pg. 334:
He wrote to his friend the motion-picture director Paul Bern, who was taking an active interest in the Mooney case: “It looks now as if you had cast your lot with a lost cause, but you and I know that lost causes are the only ones worth while.”
 
OCLC WorldCat record
The wheel spins; a novel
Author: Ethel Lina White
Publisher: New York and London, Harper & Bros., 1936.
Edition/Format:  Book : Fiction : English