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.