When I wrote this I quoted from memory, after many years had elapsed from my reading the passage. A learned friend has found it, and it is as follows:

"The ethical character is the same; both exercise despotism over the better class of citizens; and decrees are in the one, what ordinances and arrests are in the other: the demagogue too, and the court favourite, are not unfrequently the same identical men, and always bear a close analogy — and these have the principal power, each in their respective forms of government, favourites with the absolute monarch and demagogues with a people such as I have described."
—Arist. Politic. lib. iv. cap. 4.