July 17 was a day of both wins and losses for the centralizing cause. It was on this day that the federal veto was decisively defeated. In the wake of its defeat, Luther Martin was willing to throw a bone to the losing side. He proposed a supremacy clause closely modeled on the one in the New Jersey Plan. Considering that this clause would become so controversial during the ratifying debates and beyond, it is curious that the supremacy clause was agreed to unanimously and without debate or discussion. Although the wording would change slightly by the end of the summer, no one objected to its inclusion. But at this stage in the Convention, the supremacy clause must have seemed like an uncontroversial matter. From the perspective of the defenders of states’ rights, this clause merely stated what they were perfectly ready to concede: that the federal laws—when they were “made by virtue and in pursuance of the Articles of Union”—would be supreme over the state laws. They had no fear that this clause, when properly construed, would endanger the states. Their fears had been concentrated on two features of the Virginia Plan that had, more than anything else, seemed to strike a mortal blow to state sovereignty. They were fighting against a federal power to overturn state legislation (the federal veto, which had just lost); and they were fighting against a broad, indefinite grant of powers that could potentially swallow up all state powers (and this feature was still in play). By comparison to these two great issues affecting state sovereignty, the supremacy clause—which had originally formed a part of the New Jersey Plan, after all—must have seemed like a small concession to them.
What happened next was one of those great curiosities of the Convention. The Committee of Detail which met between July 27 and August 6—the same one that had inserted, on its own initiative, certain prohibitions on state powers—decided also to enumerate the powers that should be granted to Congress. This unilateral decision was all the more surprising since a motion to commit this question had already lost among the delegates only a couple of weeks earlier. Nonetheless, there must have been a tacit expectation among the delegates that this committee would attempt to specify and enumerate congressional powers, because no one at the Convention objected to this assertive insertion, and no one tried to reassert the broad indefinite powers under which they had been operating throughout that summer. Over the remaining weeks, specific powers would be added, changed, or removed from the Committee’s original enumeration, but no one tried to undo the enumeration itself.
The Committee of Detail did something else that was noteworthy. After naming more than a dozen powers that would be granted to Congress, the enumeration concluded by specifying that the legislature shall have the power “to make all laws that shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this Constitution in the government of the United States, or in any department or office thereof.” The “necessary and proper” clause would later become enormously controversial. Antifederalists seized upon this clause as proof that the federal government was really under no restraints at all. In the Virginia Ratifying Convention, opponents to the Constitution called it the “sweeping clause,” because they claimed it would sweep all powers before it. And in the first years after the Constitution was ratified, disagreements over how to interpret this clause would be a major cause of the split into a two-party system.