It has been decades since I last read Book 8 of Plato's Republic, wherein Socrates describes the deterioration of the ideal society (and in individual terms the corresponding degeneration of the character of the philosopher). Of course, Plato's analysis was primarily philosophical and psychological and only incidentally historical. The chronological sequence of the inherently inevitable decline of states from the best to the worst, from aristocracy through democracy to tyranny, is obviously more an explanatory device than a rigidly precise historical formula. Still there was a certain historically recognizable logic to the sequence, as subsequent students of the subject could see. And so it was to arrest this seemingly inexorable process that the theory of the "mixed" constitution came to be articulated - from its ancient theorists Aristotle and Polybius to the modern founders of the American constitutional experiment. Primarily, such theories sought their inspiration less from an external, ideational, philosophical analysis of human character and more from contingent political experience itself, making the best of the actual human situation, restructuring it institutionally. What Aristotle had theorized, Polybius recognized in the institutional constraints (what we Americans would come to call "checks and balances") of the Roman Republic. The 18th century American founding followed this tradition, and James Madison in The Federalist explicitly invoked both Polybius and the image of the "mixed" constitution.
But while the "mixed" constitution could certainly slow down the process of decline into tyranny, it still presumed something from its citizens - certainly not the philosophical detachment of Platonic guardians, but a certain sort of commitment to participate in the process and engage with one's fellow citizens within the parameters proposed by those "mixed" institutions - participation and engagement made possible precisely by trust in those institutions. In the American constitutional settlement (both at its founding and as subsequently amended), the perversion of pubic good by private interest always lurks in the foreground. The public or common good depends for its primacy on the the institutional restraints on populist democracy incarnated in constitutional government - made possible by citizens' inevitably imperfect but still sufficient trust in a shared community.
It is arguable that such trust in a commonly shared community may have reached its height in the collective experience of the World War II "Greatest Generation," and that the last 50 or so years have been characterized by its definitive decline. Perhaps the tipping point may have been the disastrous election of 1980, when citizenship seemed increasingly superseded by consumerism. In any case, our country's current crisis, with its suggestion of democratic devolution into increasingly unchecked and unbalanced tyranny, has been years, decades, in the making.