To quote an old post of mine:
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IMO the real founder of the Democratic Party was not Andrew Jackson but Martin Van Buren.
Van Buren thought that the disappearance of the Federalists and Monroe's policy of "amalgamation"--adopting many old Federalist policies, appointing some ex-Federalists to office, etc.--was a disaster because as he explained to Thomas Ritchie, "Political combinations between the inhabitants of the different states are unavoidable & the most natural &, beneficial to the country is that between the planters of the South and the plain Republicans of the North. The country has once flourished under a party thus constituted & may again. It would take longer than our lives (even if it were practicable) to create new party feelings to keep those masses together. If the old ones are suppressed, geographical divisions founded on local interests or, what is worse, prejudices between free & slaveholding states, will inevitably take their place. Party attachment in former times furnished a complete antidote for sectional prejudices by producing counteracting feelings. It was not until that defence had been broken down that the clamour agt. Southern influence and African Slavery could be made effectual in the North. Those in the South who assisted in producing the change are, I am satisfied, now deeply sensible of their errour.… Formerly, attacks upon Southern Republicans were regarded by those of the North as assaults upon their political brethren and resented accordingly. This all powerful sympathy has been much weakened, if not, destroyed by the amalgamating policy of Mr. Monroe. It can & ought to be revived..."
http://vanburenpapers.org/content/mvb-thomas-ritchie-13-january-1827
In other words, the Republican/Federalist conflict had to be artificially re-created; if there were no Federalists any more, J. Q. Adams had to be portrayed as one. (Of course Van Buren would have denied that there was anything artificial about it, and may have sincerely believed that the younger Adams was a Federalist at heart. ) Jackson was simply the ideal vehicle Van Buren found for this purpose (he had previously supported Crawford, but now Crawford's health made his presidential prospects impossible), and if Jackson hadn't been around, Van Buren and his associates would have found another. Which of course is not to say that Jackson was Van Buren's or anyone else's tool, but the Democratic party would have come into existence even without him.
(Incidentally, Robert Pierce Forbes in his
The Missouri Compromise and Its Aftermath, pp. 214-15 has a scathing attack on Arthur Schlesinger, Jr., Robert Remini, Sean Wilentz, etc.--"the neo-progressive school" as Ronald Formisano called it--for downplaying the role of slavery in the formation of the Jackson coalition. "One is at a loss to know just what contemporary politicians would have had to write in order to convince Remini and others of his school that slavery represented a central issue, if not
the central issue, of national politics at this time. Alternatively, one is left to wonder whether the modern chroniclers of the Democracy are not still engaged in the same project of distracting attention from the issue by means of artificial class appeals as their historical subjects--and if so, why."
https://books.google.com/books?id=lPR28UNIXgEC&pg=PA215)
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Of course that post doesn't answer who Van Buren would support in the absence of Crawford (for health reasons) and Jackson. Calhoun had now repudiated his earlier nationalism too thoroughly and was too extreme on opposition to the tariff. Thomas Hart Benton (who supported the Tariff of 1828 despite msigivings simply because it was popular in Missouri) was one possibility--he had taken the lead in opposing Adams on the Panama Conference, which helped his popularity in the South.