This chapter argues that Benjamin Constant’s greatest legacy to liberalism was his theory of parliamentarism, which revolutionized the way that the constitutional model was understood. Unlike previous authors examined in this book, Constant envisioned a constitutional monarch divested of executive powers–who reigned but not govern–and minsters who maintained their position entirely through the process of debate that unfolded within Parliament and the public sphere. Constant believed that this (seemingly) minimal framework of checks was sufficient to prevent Parliament from becoming tyrannical. It could achieve the great promise of the English parliamentary model–a nation being truly governed by a representative assembly–while at the same time overcoming the dilemmas long associated with that model, including the dilemma of corruption. The first part of the chapter examines Constant’s constitutional theory. The second part examines Constant’s involvement in French parliamentary politics during the Restoration when he tried and failed to enact this theory.