I’m not an old, experienced hand at politics. But I am now seasoned enough to have learned that the hardest thing about any political campaign is how to win without proving that you are unworthy of winning.

Adlai Stevenson (1900–1965) American diplomat, statesman

Speech (1956-06-02), Fresno, California
    (Source)

I cannot find a contemporary, primary report of this quotation. This the text as quoted in Herbert Joseph Muller, Adlai Stevenson : A Study in Values , ch. 8 (epigraph) (1967). It was also so quoted in memorium to Stevenson in Life Magazine (1965-07-23), citing it to 1956-06.

The speech was made in the lead-up to the California presidential primary (1956-06-05), when Stevenson was running against Estes Kefauver. The date for this speech is not confirmed, but extrapolated by the search hit of its text on the 1956-06-03 issue of the Santa Barbara News-Press (contents locked).

Some sources cite the quote as being from 1956-10-11; while it is possible Stevenson repeated the line at a later speech (in Fresno), he infamously disliked using set campaign text.

A variant of the quote is also given in The Atlanta Constitution (1956-06-19), in a Roscoe Drummond syndicated column (which can be found in other contemporary newspapers):

Now I'm old and seasoned and the lesson I have learned is that the hardest thing about such a campaign is how to win without proving unworthy of winning.