Timothy Sandefur’s edifying review of the shift in legal thought on the Supreme Court during the era of President Franklin Roosevelt’s progressive revolution points, among other things, to the way in which political groupings do not draw straight lines across history, such that a conservative or progressive today would have agreed with their supposed forerunners:

For a legislature to exert power in this way — for the personal benefit of the lawmaker or his allies — would be to act arbitrarily; to exert its mere will. But the due-process-of-law clause allows states to act only pursuant to law — that is, general rules serving the public good. In 1874, less than a decade after the Fourteenth Amendment added a new “due process of law” clause to the Constitution, the Court held that states could not take property from some citizens to benefit others because such legislation was not “law,” but “a decree under legislative forms.” Legislation restricting freedom only to enrich a particular faction, or lacking any basis other than legislative say-so, abridges liberty without due process of law.
Progressive-era lawyers recognized that this legal doctrine was among the most serious obstacles to redistributive legislation. They therefore formulated a theory that the due-process clause required only fair procedures, and that the constitutional prohibition on legislative arbitrariness — which they derisively labeled “substantive due process” — had been concocted by “activist” judges who merely enforced their individual political views from the bench. The judges of a previous generation would have been stunned by this accusation, but by the 1930s, it had become common in the legal academy and among younger lawyers. The clash between the two interpretations of the due-process clause would form one of the central dramas of the New Deal decade.

As it happens, I agree with the progressives, as described in the above. Within the boundaries of the Constitution, states ought to be able to be given maximal leash, with residents never deprived of the right to work to change policies or to leave, and the expectation that state governments that choose poorly will watch productive residents leave and take the health of the local society with them. The problem is that federalism turned out to be an argument of convenience for factions outside of the judicial majority.
The insight of the progressives in the text that I’ve just quoted was that there exist rules laid out in the law concocted by people in a system of self government and that the people could therefore change them. Experiment. In terms of government, there isn’t some abstract, pure Law to which legislatures and jurists must hew, because that abstraction turns out to be suspiciously similar to the opinions of the ruling class. But once they gained the majority, the progressives set about undermining the rules that made possible the very notion of due process:

… the Constitution explicitly bars states from “impairing the obligation of contracts,” a prohibition adopted in response to uprisings like the 1786 Shays’s Rebellion, in which farmers mobbed foreclosure sales, closed courts, and demanded “debtor stay laws” like that enacted in Minnesota. Laws limiting lenders’ ability to recover from defaulting borrowers dry up credit and stifle economic expansion, which is why James Madison described them as “wicked” and “contrary to the first principles of the social compact.” Even law professor William Prosser, who helped Minnesota legislators write the law, confessed in 1934 that the contracts clause “was inserted in the Constitution for the purpose of preventing precisely [this] type of legislation.”
When a bank foreclosed on the Blaisdell family’s boarding house, they sought to extend the redemption period. The judge refused, finding the law unconstitutional, but the Blaisdells appealed, and the Supreme Court upheld the law in a 5–4 decision. Admitting it could not be reconciled with the Constitution, Chief Justice Charles Evans Hughes nevertheless held that the law was justified by the economic “emergency.” It was “no answer,” he claimed, “to insist that what the provision of the Constitution meant to the vision of that day it must mean to the vision of our time.” To say “that the great clauses of the Constitution must be confined to the interpretation which the framers, with the conditions and outlook of their time, would have placed upon them” simply “carrie[d] its own refutation.”

With legislatures thus freed to to do anything, provided it coincided with the ideologies and opinions of a majority of Supreme Court justices, the deterioration of the American experiment began in earnest. In our day, the federal government has stepped up its own involvement — from minimum wages to, now, healthcare — making real due process — the ability to organize and work for change in response to unjust laws — that much more difficult, and the decision of our rulers that much more arbitrary.