A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.
—Despite the urban legend that this was written by a guy named Alexander Tytler, no one seems to know its provenance. That doesn't make it any less true.