You know, the more you read and observe about this Politics thing, you got to admit that each party is worse than the other. The one that’s out always looks the best.

Will Rogers (1879-1935) American humorist

Column (1922-12-31), “Weekly Article: Breaking into the Writing Game”
    (Source)

Reprinted in The Illiterate Digest (1924)

Often paraphrased along the lines of, "The more you observe politics, the more you've got to admit that each party is worse than the other."