When did the progressives realize they needed to specifically target the commerce clause?

Social reform requires big government. Big government requires an obedient court, which fosters a "living constitution". In "Social reform and the Constitution", progressive reformer Frank Johnson Goodnow wrote the following regarding the courts: (page 31)

The result is that the constitutional law of the country is not, either necessarily or actually, uniform. For a state court may declare unconstitutional from the point of view of the federal constitution an act of a state legislature which would have been regarded as constitutional by the United States Supreme Court. If, therefore, the state courts are more conservative than the Supreme Court, and many believe they are, they determine finally what is, in a particular state, the effect of the limitations of the federal constitution upon state action. This condition of things is, however, not one which need be permanent, nor one which can be changed only through constitutional amendment. For the jurisdiction of the federal courts is in these matters entirely within the control of Congress, which may constitutionally provide, if it sees fit to do so, that all cases both civil and criminal involving a federal question may be removed to the federal courts, and that appeals may go to the Supreme Court from all decisions of the state courts of last instance, whether they affirm or not the constitutionality of state laws.

Therefore, from a constitutional point of view, the attitude of the Supreme Court of the United States is the only really important thing to consider when we are treating of the permanent constitutional obstacles to social reform in the United States. On that account, what will be said as to the effect on the possibilities of such reform of the limitations contained in the federal constitution will in the main be confined to a consideration of the attitude of the Supreme Court towards these questions.

Our attention will naturally be directed, first to an examination of the powers of the Congress of the United States, as they are to be derived from a consideration of the provisions of the constitution as interpreted by the Supreme Court, and particularly to those clauses which contain the power to regulate commerce and the judicial power. For it is almost only through the exercise of these powers that any great centralization of our government may be secured.

This is something that progressives have long known, and it is exactly why the devised the scheme of a "living constitution". The supreme court is their holy grail institution for enforcing views upon Americans that Americans do not want and would not vote for on election day. Woodrow Wilson and others have plainly written about the need to get the courts separated from the Constitution and interpreting it in ways never intended.

Subvert and destroy. The progressives knew fully well what they had to do. And their primary target? The commerce clause. This book was written in 1911, only three years after Woodrow Wilson first floated the idea that the constitution should be reinterpreted as a living thing.

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