The determinants of support for European integration and the European Union have been analysed by previous research from a comparative perspective: factors that help to explain the differences between the levels of support of the EU member states are considered to be the factors that drive EU support in general. This article takes a different approach using a cross-time perspective to identify the sources of EU support and to investigate the causal structure of the effects. We analyse German support for European integration which is very volatile over time and test potential explanations for these fluctuations. Three bundles of factors are considered: the economy, the increasing scope of EU policies, and the domestic political process. It appears that all three are associated with fluctuations of German support for European integration. However, domestic politics seems to be mightier than often understood. The empirical evidence that is presented in support of these claims is taken from the Mannheim Eurobarometer Trendfile and recent Eurobarometer surveys, from the Comparative Political Data Set, and from the official handbook of the Bundestag.