American Constitution and Power

Is the American Constitution a counter-majoritarian or a democratic document? Explain how it fits Aristotle’s design for a mixed republic. How does our constitution serve as a barrier to popular majorities and protect the power of elites? Are constitutional checks on Presidential power still relevant under the extra-ordinary conditions of the Long War Against Terrorism? Or is the Constitution less and less relevant to how executive power is exercised in an America where the President can order military strikes on US territory or to arbitrarily detain and torture anyone suspected of being an enemy of the state? What would have Aristotle have called a system where the President has unlimited war powers not subject to court challenges?