From James Madison, Father of the Constitution:
It appears to your committee to be a plain principle, founded in common sense, illustrated by common practice, and essential to the nature of compacts, that, where resort can be had to no tribunal, superior to the authority of the parties, the parties themselves must be the rightful judges in the last resort, whether the bargain made has been pursued or violated. The Constitution of the United States was formed by the sanction of the states, given by each in its sovereign capacity. It adds to the stability and dignity, as well as to the authority of the Constitution, that it rests on this legitimate and solid foundation. The states, then, being the parties to the constitutional compact, and in their sovereign capacity, it follows of necessity, that there can be no tribunal above their authority, to decide in the last resort, whether the compact made by them be violated; and, consequently, that, as the parties to it, they must themselves decide, in the last resort, such questions as may be of sufficient magnitude to require their interposition.
But I forget. He wasn't a Republican, so what does he know.
"The nullifiers it appears, endeavor to shelter themselves under a distinction between a delegation and a surrender of powers. But if the powers be attributes of sovereignty & nationality & the grant of them be perpetual, as is necessarily implied, where not otherwise expressed, sovereignty & nationality are effectually transferred by it, and the dispute about the name, is but a battle of words. The practical result is not indeed left to argument or inference. The words of the Constitution are explicit that the Constitution & laws of the U. S. shall be supreme over the Constitution and laws of the several States; supreme in their exposition and execution as well as in their authority. Without a supremacy in those respects it would be like a scabbard in the hands of a soldier without a sword in it. The imagination itself is startled at the idea of twenty four independent expounders of a rule that cannot exist, but in a meaning and operation, the same for all.
"The conduct of S. Carolina has called forth not only the question of nullification; but the more formidable one of secession. It is asked whether a State by resuming the sovereign form in which it entered the Union, may not of right withdrasw from it at will. As this is a simple question whether a State, more than an individual, has a right to violate its engagements, it would seem that it might be safely left to answer itself. But the countenance given to the claim shows that it cannot be so lightly dismissed. The natural feelings which laudably attach the people composing a state, to its authority and importance, are at present too much excited by the unnatural feelings, with which they have been inspired agst. (sic) their bretheren of other States, not to expose them, to the dangers of being misled into erroneous views of the nature of the Union and the interest they have in it. One thing at least seems to be too clear to be questioned; that whilst a State remains within the Union it cannot withdraw its citizens from the operation of the Constitution & laws of the Union. In the event of an actual secession without the Consent of the Co-States, the course to be pursued by these involves questions painful in the discussion of them. God grant that the menacing appearances, which obtrude it may not be followed by positive occurrences requiring the more painful task of deciding them!"
-- James Madison, March, 1833
Walt