“If you can’t convince them, confuse them”

“If you can’t convince them, confuse them” was popularized in 1948 by U.S. President Harry S. Truman (1884-1972), referring to the tactics of the opposition Republican party. Truman said on September 18, 1948:
 
“It’s an old political trick. ‘If you can’t convince them, confuse them.’ But this time it won’t work.”
 
Truman repeated the line in October 1948:
 
“I don’t think you are going to be victims this time of the old Republican doctrine: ‘If you can’t convince them, confuse them.’”
 
The “if you can’t convince them, confuse them” doctrine may be old, but there is no evidence that it is exclusively Republican. “If you can’t convince a man by your argument you can always silence him by quoting a lot of statistics that he knows absolutely nothing about,” cited in 1900 by The Evening Star (Washington, DC), was from a “man who talks on politics.”
 
“If you can’t dazzle them with brilliance, baffle them with bullshit” is a similar saying.
 
     
Wikiquote: Harry S. Truman
Harry S. Truman (May 8, 1884 – December 26, 1972) was the thirty-third President of the United States (1945–1953); as vice president, he succeeded to the office upon the death of Franklin D. Roosevelt.
 
Quotes
(...)
On the one hand, the Republicans are telling industrial workers that the high cost of food in the cities is due to this government’s farm policy. On the other hand, the Republicans are telling the farmers that the high cost of manufactured goods on the farm is due to this government’s labor policy.
 
That’s plain hokum. It’s an old political trick: “If you can’t convince ‘em, confuse ‘em.” But this time it won’t work.
. Address at the National Plowing Match (18 September 1948); as quoted in Miracle of ‘48: Harry Truman’s Major Campaign Speeches and Selected Whistle-stops (2003); edited by Steve Neal. Truman’s mention of an “old political trick” is often quoted alone as if it were a strategy he was advising rather than one he was criticizing.
   
Chronicling America
11 October 1900, The Evening Star (Washington, DC), pg. 6, col. 3:
Mathematics.
“There is safety in numbers,” said the trite conversationalist.
 
“There is,” answered the man who talks on politics. “If you can’t convince a man by your argument you can always silence him by quoting a lot of statistics that he knows absolutely nothing about.”
 
19 September 1948, Richmond (VA) Times-Dispatch, “President Says ‘Gluttons of Privilege’ Back GOP,” pg. 21, col. 5:
“It’s an old political trick. ‘If you can’t convince them, confuse them.’ But this time it won’t work.”
(Spoken by President Harry S. Truman.—ed.)
 
19 October 1948, Evening World-Herald (Omaha, NE), “‘Hoover Cart’ Truman Target,” pg. 11, col. 3:
Raleigh, N. C. (AP)—Partial text of President Truman’s address prepared for the North Carolina State Fair Tuesday:
(...)
I don’t think you are going to be victims this time of the old Republican doctrine: “If you can’t convince them, confuse them.”
 
Google News Archive
21 December 1950, Pittsburgh (PA) Press, “Letters to the Editor,” pg. 20, col. 5:
I suppose the old adage is true: If you can’t convince them, confuse them.
JOHN ERBEN.
400 Collins Ave.
 
5 July 1955, The Times-Picayune (New Orleans, LA), “Up and Down the Street” by the Want-Ad Reporter, pg. 15, col. 2:
“If You Can’t Convince ‘Em, Confuse ‘Em,” suggests another sign.
 
20 July 1964, Richmond (VA) Times-Dispatch, “Show Time” by Earl Wilson, pg. 35, col. 1:
WISH I’D SAID THAT: Some of the political convention tactics recall Will Rogers’ advice: “If you can’t convince ‘em, confuse ‘em.”
 
Google News Archive
10 June 1971, The Southeast Missourian (Cape Girardeau, MO), “Hearnes-{ierce debate sheds little light on state money woes" by John G. Adney, pg. 1, col. 5:
Accusing Rep. Pierce of making "misleading" and "false" statements, the governor said: "It's the old story…if you can't convince them, confuse them."

Google Books
Get ‘Em Laughing:
Public Speaking Humor, Quotes and Illustrations
By E. Gene Davis
Victoria, BC: Trafford Publishing
2007
Pg. 73:
If you can’t convince them, confuse them.
President Harry S. Truman
   
Google Books
The Official Rules:
5,427 Laws, Principles, and Axioms to Help You Cope with Crises, Deadline, Bad Luck, Rude Behavior, Red Tape, and Attacks by Inanimate Objects
By Paul Dickson
Mineola, NY: Dover Publications, Inc.
2013
Pg. 353:
Truman’s Law: If you can’t convince them, confuse them. (Harry S Truman; Co.)