John Calhoun, shortly before his death in 1850, urged (in his *Discourse on the Constitution and Government of the United States*) that there be two presidents, one elected by the North, one by the South; he thought this the only way to check the increasing power of the North, which unless checked would ultimately be fatal either to the Union or to slavery:
"How the constitution could best be modified, so as to effect the object, can only be authoritatively determined by the amending power. It may be done in various ways. Among others, it might be effected through a reorganization of the executive department; so that its powers, instead of being vested, as they now are, in a single officer, should be vested in two--to be so elected, as that the two should be constituted the special organs and representatives of the respective sections, in the executive department of the government; and requiring each to approve all the acts of Congress before they shall become laws. One might be charged with the administration of matters connected with the foreign relations of the country--and the other, of such as were connected with its domestic institutions; the selection to be decided by lot. It would thus effect, more simply, what was intended by the original provisions of the constitution, in giving to one of the majorities composing the government, a decided preponderance in the electoral college--and to the other majority a still more decided influence in the eventual choice--in case the college failed to elect a President. It was intended to effect an equilibrium between the larger and smaller States in this department--but which, in practice, has entirely failed; and, by its failure, done much to disturb the whole system, and to bring about the present dangerous state of things.
"Indeed, it may be doubted, whether the framers of the constitution did not commit a great mistake, in constituting a single, instead of a plural executive. Nay, it may even be doubted whether a single chief magistrate--invested with all the powers properly appertaining to the executive department of the government, as is the President--is compatible with the permanence of a popular government; especially in a wealthy and populous community, with a large revenue and a numerous body of officers and employees. Certain it is, that there is no instance of a popular government so constituted, which has long endured. Even ours, thus far, furnishes no evidence in its favor, and not a little against it; for, to it, the present disturbed and dangerous state of things, which threatens the country with monarchy, or disunion, may be justly attributed. On the other hand, the two most distinguished constitutional governments of antiquity, both in respect to permanence and power, had a dual executive. I refer to those of Sparta and of Rome. The former had two hereditary, and the latter two elective chief magistrates. It is true, that England, from which ours, in this respect, is copied, has a single hereditary head of the executive department of her government--but it is not less true, that she has had many and arduous struggles, to prevent her chief magistrate from becoming absolute; and that, to guard against it effectually, she was finally compelled to divest him, substantially, of the power of administering the government, by transferring it, practically, to a cabinet of responsible ministers, who, by established custom, cannot hold office, unless supported by a majority of the two houses of Parliament. She has thus avoided the danger of the chief magistrate becoming absolute; and contrived to unite, substantially, a single with a plural executive, in constituting that department of her government. We have no such guard, and can have none such, without an entire change in the character of our government; and her example, of course, furnishes no evidence in favor of a single chief magistrate in a popular form of government like ours--while the examples of former times, and our own thus far, furnish strong evidence against it.
"But it is objected that a plural executive necessarily leads to intrigue and discord among its members; and that it is inconsistent with prompt and efficient action. This may be true, when they are all elected by the same constituency; and may be a good reason, where this is the case, for preferring a single executive, with all its objections, to a plural executive. But the case is very different where they are elected by different constituencies--having conflicting and hostile interests; as would be the fact in the case under consideration. Here the two would have to act, concurringly, in approving the acts of Congress--and, separately, in the sphere of their respective departments. The effect, in the latter case, would be, to retain all the advantages of a single executive, as far as the administration of the laws were concerned; and, in the former, to insure harmony and concord between the two sections, and, through them, in the government. For as no act of Congress could become a law without the assent of the chief magistrates representing both sections, each, in the elections, would choose the candidate, who, in addition to being faithful to its interests, would best command the esteem and confidence of the other section. And thus, the presidential election, instead of dividing the Union into hostile geographical parties, the stronger struggling to enlarge its powers, and the weaker to defend its rights--as is now the case--would become the means of restoring harmony and concord to the country and the government. It would make the Union a union in truth--a bond of mutual affection and brotherhood--and not a mere connection used by the stronger as the instrument of dominion and aggrandizement--and submitted to by the weaker only from the lingering remains of former attachment, and the fading hope of being able to restore the government to what it was originally intended to be, a blessing to all.
"Such is the disease--and such the character of the only remedy which can reach it. In conclusion, there remains to be considered, the practical question--Shall it be applied? Shall the only power which can apply it be invoked for the purpose?
"The responsibility of answering this solemn question, rests on the States composing the stronger section. Those of the weaker are in a minority, both of the States and of population; and, of consequence, in every department of the government. They, then, cannot be responsible for an act which requires the concurrence of two-thirds of both houses of Congress, or two-thirds of the States to originate, and three-fourths of the latter to consummate. With such difficulties in their way, the States of the weaker section can do nothing, however disposed, to save the Union and the government, without the aid and co-operation of the States composing the stronger section: but with their aid and co-operation both may be saved. On the latter, therefore, rests the responsibility of invoking the high power, which alone can apply the remedy--and, if they fail to do so, of all the consequences which may follow..."
http://www.constitution.org/jcc/dcgus.htm
Ironically, had Calhoun's system been adopted in the 1850s it might actually have hurt the slaveholding states, [1] since the northern president might veto the Fugitive Slave Act and the Kansas-Nebraska Act. (Though I'm not so sure about that; remember that Pierce swept the North as well as the South in 1852. Still, even in OTL Pierce had his reservations about the Kansas-Nebraska Act at first, and if he knew he were dependent *solely* on northern votes for re-election, he might have been a very different president. Assuming of course that he got nominated in the first place--after all, much of his support for the nomination in 1852 was from the South.)
[1] One could of course argue that the slaveholders would have been a lot better off had not such "pro-slavery" measures as the Fugitive Slave Law and the Kansas-Nebraska Act been passed, since the resentments these laws caused in the North easily outweighed whatever dubious things the laws accomplished for the "peculiar institution." But that is not how most Southerners saw it at the time, Sam Houston and John Bell being exceptions in the case of the K-N Act.