The tumultuous events of the New Deal Era did not take place in a vacuum, however. They grew out of the intellectual work of the Progressive Era, which inaugurated the fundamental shift in American constitutional thought. The Progressives were the self-conscious social and legal reformers who occupied center stage in the period roughly from the onset of the 20th century through the election of Franklin Delano Roosevelt as president in 1932. They exerted a considerable influence on legal and constitutional theory in the years before Roosevelt took over the presidency. In addition, most of the innovative, if controversial, domestic programs of the New Deal were in fact direct outgrowths of the Progressive campaign for larger, more active government during the 30-plus years preceding the watershed events of 1937.
To understand the importance of the Progressive movement to modern constitutional theory and politics, one might find useful a summary of its key social and legal positions, most of which were articulated in opposition to the dominant social and legal thought of the Old Court—"old" as in antiquated or outdated—whose principles it successfully displaced. First, as a general matter, Progressives believed in the power of science and economics, employed by government, to lift up the economic and social position of the general population. In this regard, they were influenced in part by Bismarckian social initiatives in 19th-century Germany, which had pioneered various forms of worker protection and social insurance. Second, to achieve their expansive social ends, Progressives adopted a "realist" jurisprudence that broke sharply from the then-dominant "formalist" approach to law, which they dismissed as "blind" to the massive power shifts in social relations that took place with industrialization following the Civil War.
(Richard A. Epstein, How Progressives Rewrote the Constitution [Washington, DC: Cato Institute, 2006], 2-3)
Keith Burgess-Jackson, J.D., Ph.D. 