Polybius or Patrick Deneen?
For when a state, after having passed with safety through many and great dangers, arrives at the highest degree of power, and possesses an entire and undisputed sovereignty; it is manifest that the long continuance of prosperity must give birth to costly and luxurious manners, and that the minds of men will be heated with ambitious contests, and become too eager and aspiring in the pursuit of dignities. And as these evils are continually increased, the desire of power and rule and the imagined ignominy of remaining in a subject state, will first begin to work the ruin of the republic; arrogance and luxury will afterwards advance it: and in the end the change will be completed by the people; when the avarice of some is found to injure and oppress them, and the ambition of others swells their vanity, and poisons them with flattering hopes. For then, being inflamed with rage and following only the dictates of their passions, they no longer will submit to any control, or be contented with an equal share of the administration, in conjunction with their rulers; but will draw to themselves the entire sovereignty and supreme direction of all affairs. When this is done, the government will assume indeed the fairest of all names, that of a free and popular state; but will in truth be the greatest of all evils, the government of the multitude.
The General History of Polybius, translated by James Hampton (fifth edition, vol. II., Oxford: W. Baxter, 1823), 178-79.