Could it be this quote from Dune?
Democracy is susceptible to being led astray by having scapegoats paraded in front of the electorate. Get the rich, the greedy, the criminals, the stupid leader and so on ad nauseam.
Or this one, from Chapterhouse: Dune?
The downfall of democracy is the tyranny of the minority cloaked in the mask of the majority, where it is either overthrown by its own excesses or eaten away by bureaucracy. First, a Civil Service law masked in the lie that it is the only way to correct demagogic excesses and spoils systems. Then the accumulation of power in places the voters could not touch. And finally, aristocracy.