This paper analyzes the performative impact of the European Commission's model for estimating 'potential output', which is used as a yardstick for measuring the 'structural budget balance' of EU countries and, hence, is crucial for coordinating European fiscal policies. In pre-crisis years, potential output estimates amplified the build-up of private debt, housing bubbles and macroeconomic imbalances. After the financial crisis, they were revised downwards, which increased fiscal consolidation pressures. By focusing on the euro area's economies during 1999-2014, we identify two performative aspects of the potential output model. First, the political implications of the model led to a pro- cyclical feedback loop, reinforcing general economic developments. Second, the model has contributed to national lock-ins on path dependent debt trajectories, fueling 'structural polarization' between core and periphery.