The ECB as a political actor: a ‘fourth branch’ of government?

This paper takes as a starting point the ECB’s evolving role in the EMU since the Eurozone crisis. Firstly, it explores the extent to which the ECB’s role has de facto expanded – even though its primary objective has remained intact at the formal legal level (maintaining price stability) – and has turned the ECB into a political actor in the EMU’s constitutional framework (into the “de facto existential guarantor or economic sovereign of the Euro area” in Tucker’s words) despite it being a technocratic institution. Secondly, it examines whether this expansion of the ECB's role has unsettled the formal allocation of competences between the EMU and its Member States, given the impact of the ECB’s discretionary power on the Member States' fiscal policy (and the broad discretion that the CJEU has attributed to the ECB in Weiss and Gauweiler). Has this turned the ECB into a de facto “independent fourth branch” of government of the member states (possibly along with other EU institutions)?