["JCMS: Journal of Common Market Studies, Volume 64, Issue 4, Page 1359-1381, July 2026. ", "\nABSTRACT\nImportant Projects of Common European Interest (IPCEIs) have become a central tool of the European Union's (EU) new industrial policy. IPCEIs derive their peculiar name from an exemption to the general prohibition on state aid that has existed since the Treaty of Rome but has only led to the creation of a stand‐alone policy instrument in 2014. In this paper, we introduce the concept of institutional activation to shed light on both the origins and evolution of this Treaty article. We reconstruct how the article reflected a compromise between different coalitions during the Treaty negotiations; how it remained largely dormant in the absence of a sustained coalitional push to activate it; and how it was finally activated by a coalition of institutional entrepreneurs' intent on using the article's untapped potential for new forms of industrial policy.\n"]