A Lack of Education and Cultivation
One of the prerequisites for democracy is an educated and cultured population (see chapter Education, Cultivation, Paideia, Bildung). Education in the form of professional knowledge is not enough. Democracy can only be sustained by a population which has a cultural ballast, which has a practice of open debate and which is not afraid of otherness, but is capable of showing tolerance. One of the threats to democracy, of course, is when this cultivation disappears or perhaps has never been present.
That there must be liberal education, culture and debate does not mean that all 100% of the population have to be active in the debate or creating cultural events - in that case, most democracies would have perished long ago! However, there has to be a critical mass of people who have historical knowledge, cultural insight and philosophical routine and are otherwise broadly informed about how the world hangs together for the debate to be kept to a factual level. There is also a need for widespread recognition that all this knowledge and culture is important.
Without both depth and breadth, the debate descends into mudslinging and isolated allegations, and that is not a situation in which one can build a healthy political society.
Next chapter: The Arrogance of Might, Newspeak and Spin