Support by a segment of industrialists for Juan Perón has been a crucial feature of much writing about Peronism. This has been sustained by such diverse authors as Torcuato Di Tella, Miguel Murmis and Juan Carlos Portantiero, and Guillermo O'Donnell. Moreover, in many discussions of the nature of populism—in which Peronism is considered an epitome of the phenomenon—a critical role is played by a multiclass alliance which included both workers and industrialists. Yet in 1945 industrialists as a group did not support Perón. The year 1945 is critical to any discussion of the nature of Peronism because it was then that Perón built his core constituency. In addition, there occurred what can only be considered the founding myth of Peronism—the massive workers' demonstration of October 17. Later Perón was able to expand his support, but his base was created in 1945. In order to better understand both the development of Perón's support and then to reflect on what this tells us about the nature of populism, the relationship between Perón and industrialists will be explored from the military's seizure of power in June 1943 to the presidential elections in February 1946. During this period—although Perón was rapidly gathering power—he was not formally head of the government.