Campaign remark, Fresno, Cal., 10 Sept. 1952. John F. Parker, in "If Elected, I Promise ...": Stories and Gems of Wisdom by and About Politicians (1969), attributes the reverse statement to Chauncey Depew (1834 - 1928): "If you will refrain from telling any lies about the Republican party, I'll promise not to tell the truth about the Democrats."
Oliver Wendell Holmes (1943). “The Mind and Faith of Justice Holmes: His Speeches, Essays, Letters, and Judicial Opinions”, p.444, Transaction Publishers