Democracy: concession or perfection?

"Man's capacity for justice makes democracy possible, but man's inclination to injustice makes democracy necessary."

- Reinhold Niebuhr, The Children of Light and The Children of Darkness.

Is democracy merely a concession to human weakness or the truest expression of Christian convictions in the political sphere? Niebuhr believed that democracy had much to commend it, though he thought that the way that it was often justified in his day (the early to mid 20thC) involved overly optimistic estimations of human nature. He sought to defend democracy from its detractors while placing it on a firmer theological foundation by arguing that the checks and balances of democracy are a concession to human sinfulness.

In the early modern period, Martin Luther and Thomas Hobbes shared a deep conviction of the human capacity for and inclination towards destructive behaviours, but they thought that this necessitated an absolutist state to restrain these tendencies. Niebuhr is equally realistic in his assessment of human failings, but applied this also to political authorities. If the tendency towards selfishness is ubiquitous, then not even governing authorities are exempt. Who watches the watchers? This is why a political system that has mutual accountability built in and a separation of powers will prove slightly more corruption-resistant.
Five points for the first to identify this democratic institution.