Taken together, the enumerated powers, supremacy clause, and oaths required by state officials form a complex system of federalism that gives to Congress limited but formidable powers. And more important, the Constitution gives to the federal government the authority it needs—particularly in the office of the executive and judicial branches—to defend its powers as supreme.
It is probably safe to say that no one going into the Convention had a clear idea of what variety of federalism they would have when they came out. Instead, the more nationalistic members had wanted an unambiguous sovereignty in the central government by giving to Congress a federal veto over state laws as well as broad, indefinite powers of its own. Defenders of the state sovereignty, on the other hand, preferred to keep the structure that they had enjoyed under the Articles of Confederation; they wished to do little more than add a few powers to Congress that almost everyone agreed were needed and establish an executive and judiciary with very limited scope. What emerged at the end of the summer’s deliberations was a compromise position between the two extremes. The federal veto was dropped, but new prohibitions on state powers were added. Congressional powers were enumerated, but they were broader and more potent than those given to the Congress under the Articles of Confederation, and they were broadened even further by a “necessary and proper” clause. The federal government was further strengthened, at least on paper, by a “supremacy clause” and a requirement that state officials swear oaths to support the Constitution. But probably most important of all, the new Congress would be able to legislate for the individuals composing the Union, for example to impose taxes on people directly, not just the states in their corporate capacity, and there would be robust executive and judicial branches (the latter armed with the power of judicial review) to uphold those supreme federal laws and those prohibitions on state powers.
What the Framers had created, in fact, was a constitution that was “partly federal and partly national.” They had attempted what some had deemed impossible: to divide sovereignty between two different layers of government. Hamilton had been among those delegates who had denied the possibility of divided sovereignty in the Constitutional Convention, but in New York’s ratifying convention he changed his tune. He said that the political axiom that he had earlier defended was in fact “curious sophistry” and “false.” Under the new Constitution, “the laws of the United States are supreme,” he said, “as to all their proper, constitutional objects: the laws of the states are supreme in the same way.” In Federalist No. 33, he said that only those powers which were exercised pursuant to the constitution would be the “supreme law of the land.” Any powers that the Congress tried to exercise outside of those bounds would “be merely acts of usurpation, and will deserve to be treated as such.” Similarly, Madison explained in Federalist No. 39 that the sovereignty in the federal government extended “to certain enumerated objects only,” but the states retained “a residuary and inviolable sovereignty over all other objects.”
Hamilton and Madison did not enter the Convention with the goal of creating a divided sovereignty, but for Madison, at least, what the Framers created later became a source of pride for him. Toward the end of his life Madison wrote:
No other Government can furnish a key to [the Constitution’s] true character. Other Governments present an individual and indivisible sovereignty. The Constitution of the United States divides the sovereignty; the portions surrendered by the States composing the Federal sovereignty over specified subjects; the portions retained forming the sovereignty of each over the residuary subjects within its sphere. If sovereignty cannot be thus divided, the political system of the United States is a chimera, mocking the vain pretensions of human wisdom. If it can be so divided, the system ought to have a fair opportunity of fulfilling the wishes and expectations which cling to the experiment.
What had been the result of contention and compromise within the Convention would eventually become a shining example of American ingenuity. Making the compromises work in practice, however, would be a struggle for generations of Americans.