Institutional environments and everyday EU decision making - Rationalist or constructivist?

What difference do institutional environments make? Do they primarily affect strategy, with constraining and enabling effects on behavior as rationalists hold? Or do they also affect attitudes, identities, and how interests are formulated as constructivists assert? Within a given institutional environment, what impact does the "style" of decision making-which beyond formal characteristics such as the decision rule includes informal rules, norms, and shared understandings-play in determining bargaining outcomes? This article examines these questions in the context of EU decision making by focusing on the Committee of Permanent Representatives (Coreper). Coreper is an ideal laboratory to test these questions empirically, because this committee represents the needle's eye through which the legislative workload of the Council flows. And the permanent representatives who live in Brussels and meet weekly to prepare upcoming ministerial meetings are exemplars of state agents given their prominence in articulating and defending national interests across the gamut of EU affairs.