Ad hoc issue coalitions allow advocates to pool resources and signal support of their position to policymakers. Ad hoc coalitions, however, are not formed in every instance; groups do not always choose to ally since there are also costs associated with membership. To understand why organizations sometimes decide to ban together and sometimes choose to forge ahead alone, I argue we must consider the institutional structure of the political system; the nature of the issue at hand; and finally the

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... characteristics of the interest group itself. This theory is tested on original data based on interviews with a 149 lobbyists active on a random sample of 47 policy issues in the United States and the European Union. The results show that EU advocates are building formal coalitions at a much lower rate than their American counterparts. The qualitative evidence suggests that the democratic accountability of policymakers may explain these differences.