We investigate whether and how economic integration increases state capacity. This important relationship has not been studied in detail so far. We put together a conceptual framework that highlights what we call the Montesquieu, Weber and Smith channels to guide our analysis. Each of these corresponds to a series of mechanisms in three distinct institutional arenas: judiciary, bureaucracy and competition policy. To test our framework, we introduce a new panel of institutional reform measures that allow us to investigate how changes in these three arenas interact with each other and what sequence of changes yields increases in state capacity. The yearly data set covers all the 17 candidate countries to join the European Union (EU) after the 1995 enlargement. Deep integration, we find, can induce broad institutional change by providing incentives for simultaneous change in core state institutions. Bureaucratic independence and judicial capacity seem to be the key engine of the process engendered by the prospect of EU membership. Yet early and abrupt removal of external anchors might generate significant backsliding, or reversals, in domestic institutional change.