Integrated statewide parties can serve as a political safeguard to prevent opportunist behaviour of political actors in the federal bargain. In this article, I argue that donation levels of statewide parties’ branches offer a proxy to the intensity of regional party activity, and thereby to the extent to which statewide parties are integrated across states. Based on original data on German parties’ financial affairs from 2009 to 2017, this article examines the determinants of statewide party branches’ donation levels. The analysis finds strong effects of both state and federal elections, suggesting that, despite cooperative federalism in Germany, political competition strongly affects party activity at the subnational level. By contrast, states’ economic environment plays only marginally into income levels. Moreover, parties’ path-dependent trajectories account for asymmetries in revenue levels between Western and Eastern branches.