This chapter explores and interprets the long revolution of the 1860s (1862–1875): a ‘context-breaking liberal moment’ that featured a revolution, a Constituent Assembly, a change of dynasty, a new constitutional system and a crisis over defining the scope of parliamentary jurisdiction. During and after this moment political institutions were reconfigured and the monarchy was put on a new institutional footing. In short, the way of ‘doing’ politics was radically transformed. By paying due attention to ideas as drivers of political change and to the role of the jurists in forming these ideas, the chapter demonstrates that what ultimately made this crisis a legitimacy crisis – and indeed, gave the revolution its language – was the way in which the king’s rule increasingly came to be seen as a de facto usurpation of power that had unsettled the balance of the constitution and was breaking the contract with the nation. In other words, the critics of the monarchy were essentially building on the moderate liberal ideas that had developed in the preceding years.