In addition to the 17th Amendment, and the points made above, another turning point in our nation's history and "federalism" was reached when the "general welfare" clause of Article One, Sec. 8 of the Constitution was interpreted as a general grant of power to the federal government (advocated by Hamilton) in United States vs Butler. (1936)

Up until that time Madison's view had mostly prevailed. (See, Bailey vs. Drexel Furniture Co. (1922) - a child labor tax was an impermissible exercise of federal power under the commerce clause.) Madison wrote that the "general welfare clause" was not a separate grant of power to the federal government, but rather a limit on the taxing power and did not expand the enumerated powers in Article One, Sec. 8.

A year later in Helvering vs. Davis (1937) the court expanded the Hamiltonian view and interpreted the clause as "conferring upon Congress a plenary power to impose taxes and to spend money for the general welfare subject almost entirely to its own discretion."

http://en.wikipedia.org/wiki/General_Wel....

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"Our Constitution is designed only for a moral and religious people. It is wholly inadequate for any other." ~ John Adams