Abstract
The article introduces the theoretical perspective on gradual institutional change to the corporatization literature. This is achieved via a longitudinal case study on the institutionalization of the Danish state guarantee model (SGM) for transport infrastructure based on archival document studies of seven infrastructure projects and 31 interviews with elite actors and experts. The article explores with a detailed analysis how the gradual change mechanisms of layering, conversion and displacement coexist, are interrelated, and are coevolving over a long period. It contributes to the corporatization literature presenting the SGM as an alternative to public and private partnerships and government agencies.