Contemporaneous Counterarguments
The Anti-Federalists vigorously contested the notion that a republic of diverse interests could survive. The author Cato (another pseudonym, most likely that of George Clinton) summarized the Anti-Federalist position in the article Cato no. 3:
Whoever seriously considers the immense extent of territory comprehended within the limits of the United States, with the variety of its climates, productions, and commerce, the difference of extent, and number of inhabitants in all; the dissimilitude of interest, morals, and policies, in almost every one, will receive it as an intuitive truth, that a consolidated republican form of government therein, can never form a perfect union, establish justice, insure domestic tranquility, promote the general welfare, and secure the blessings of liberty to you and your posterity, for to these objects it must be directed: this unkindred legislature therefore, composed of interests opposite and dissimilar in their nature, will in its exercise, emphatically be, like a house divided against itself.
Generally, it was their position that republics about the size of the individual states could survive, but that a republic on the size of the Union would fail. A particular point in support of this was that most of the states were focused on one industry—to generalize, commerce and shipping in the northern states and plantation farming in the southern. The Anti-Federalist belief that the wide disparity in the economic interests of the various states would lead to controversy was perhaps realized in the American Civil War, which some scholars attribute to this disparity. Madison himself, in a letter to Thomas Jefferson, noted that differing economic interests had created dispute, even when the Constitution was being written. At the convention, he particularly identified the distinction between the northern and southern states as a "line of discrimination" that formed "the real difference of interests".
The discussion of the ideal size for the republic was not limited to the options of individual states or encompassing union. In a letter to Richard Price, Benjamin Rush noted that "Some of our enlightened men who begin to despair of a more complete union of the States in Congress have secretly proposed an Eastern, Middle, and Southern Confederacy, to be united by an alliance offensive and defensive".
In making their arguments, the Anti-Federalists appealed to both historical and theoretic evidence. On the theoretical side, they leaned heavily on the work of Charles de Secondat, Baron de Montesquieu. The Anti-Federalists Brutus and Cato both quoted Montesquieu on the issue of the ideal size of a republic, citing his statement in The Spirit of the Laws that:
It is natural to a republic to have only a small territory, otherwise it cannot long subsist. In a large republic there are men of large fortunes, and consequently of less moderation; there are trusts too great to be placed in any single subject; he has interest of his own; he soon begins to think that he may be happy, great and glorious, by oppressing his fellow citizens; and that he may raise himself to grandeur on the ruins of his country. In a large republic, the public good is sacrificed to a thousand views; it is subordinate to exceptions, and depends on accidents. In a small one, the interest of the public is easier perceived, better understood, and more within the reach of every citizen; abuses are of less extent, and of course are less protected.
Greece and Rome were looked to as model republics throughout this debate, and authors on both sides took Roman pseudonyms. Brutus points out that the Greek and Roman states were small, whereas the U.S. is vast. He also points out that the expansion of these republics resulted in a transition from free government to tyranny.
Read more about this topic: Federalist No. 10