“Never wrestle with a pig—you get dirty and the pig likes it”

“Never wrestle with a pig—you get dirty and the pig likes it” has been said to be Abraham Lincoln-esque, but there is no record that Lincoln said anything like it. The saying has been cited since at least 1946 and has been popularly used in political speech.
 
The phrase has been used in Texas, but its place of origin is unknown. Cyrus S. Ching (1876-1967), a labor union mediator and federal administrator, possibly coined the saying in the 1940s.
   
 
Wikipedia: Cyrus S. Ching
Cyrus S. Ching (May 21, 1876 – December 27, 1967) was a Canadian-American who became an American industrialist, federal civil servant, and noted labor union mediator. He was the first director of the Federal Mediation and Conciliation Service (FMCS) and the Wage Stabilization Board.
 
Google Books
Moving ahead on your job:
A guide to success in your work
By Richard P Calhoon
Toronto: Collins
1946
Pg. 171:
And when you begin refuting one another’s reasons, fussing back and forth, you generally do what a nationally known industrial relations authority warns you against: you wallow in the mud with the pig. He says, “Never wallow in the mud with a pig, because the pig likes it.” That is exactly what he wants, because you are on his home ground. He can think of arguments as well as you can, so where do you come out?
 
31 May 1948, Charleston (WV) Daily Mail, “Notes of a New York Columnist” by Walter Winchell, pg. 13, col. 5:
Some politicians were discussing hecklers. One of them said he never made reply. “Many years ago,” he explained, “my father told me never to roll in the mud with a pig. Because you both get covered with mud—and the pig likes it.”
   
Google Books
Problems in Personnel Administration
By Richard P. Calhoon
New York, NY: Harper
1949
Pg. 409:
Cyrus S. Ching once put it this way: “Don’t wallow in the mud with a pig— the pig likes it.”
 
Time magazine
THE ADMINISTRATION: Come & Get It
Monday, Oct. 23, 1950
(...)
But last week Harry Truman acted—after a fashion. He appointed cob-nosed old (74) Cyrus Ching to the high-sounding post of director of the Wage Stabilization Board, though the board did not yet exist.
 
As director of the Federal Mediation and Conciliation Service, big, pipe-smoking Cyrus Ching had stuck his lanky legs under countless negotiating tables, earned himself a reputation for homespun, amiable integrity, helped solve many a minor strike, some major ones.
(...)
“I learned long ago never to wrestle with a pig,” Ching likes to say. “You get dirty and besides the pig likes it
 
19 November 1968, Dallas Morning News, section A, pg. 1:
Commissioner Frank Crowley said he made an attempt to stay out of the controversy Monday. “Never wrestle with a greased pig,” he explained. “You can’t win and in the second place, the pig enjoys it.”
 
Google Books
The American Treasury
by Clifton Fadiman
New York: Harper & Rowe
1955
Pg. 696 (CYRUS CHING):
I learned long ago never to wrestle with a pig. You get dirty, and besides the pig likes it.
 
Google Books
The Military Quoation Book
edited by James Charlton
New York: St. Martin’s Press
2002
Pg. 95:
Never wrestle with pigs—you get dirty and they enjoy it.
CREIGHTON ABRAMS
 
Google Books
Never Wrestle With a Pig
by Mark H. McCormack
New York: Penguin Books
2002
 
Austin American-Statesman (June 7, 2007)
He was a class act with a quick — albeit deadpan — sense of humor. A sign paraphrasing Abraham Lincoln that decorated his office wall offered a humorous insight into the Davidson’s style.

“Never wrestle with a pig,” the sign advised. “You get dirty and the pig likes it.”