… is from page 173 of H.L. Mencken’s essay “The Politician,” as it is reprinted in the 1996 Johns Hopkins University Press collection of some of Mencken’s best essays, Prejudices: A Selection:
At each election we vote in a new set of politicians, insanely assuming that they are better than the set turned out. And at each election we are, as they say in the Motherland, done in.