Regardless of whether we study individual or collective actors, there is little doubt that leadership matters in politics. However, political scientists still face the problem of determining a leader’s impact on policy or institutional change. This problem regards both the conceptualization as well as the assessment of a leader’s impact: How can we know that a given policy outcome or institutional change is really caused by the leadership of a particular actor? In this paper, I argue that comparisons or counterfactuals cannot solve this problem in a satisfactory manner. In addition, we need to study the causal mechanisms by which leadership affects outcomes. The appropriate method for doing so is process-tracing. Starting from the proposition that a leader wields influence by translating power resources into particular strategies, I suggest a way to conceptualize and trace these leadership strategies. Furthermore, I illustrate the added value of this approach by applying it to EU policy-making: I analyse the leadership strategies employed by the European Central Bank (ECB) when announcing the so-called Outright Monetary Transactions and thereby suspending the eurozone crisis. The paper thus suggests a fruitful way of combining leadership studies with European integration research, and it sheds light on the strategies used by the ECB in combatting the eurozone crisis.
