Former Republican (constitutionalist) President Thomas Jefferson, in a letter to former Republican  Representative John Holmes, of the Commonwealth of Massachusetts, predicts that the Missouri Compromise line will lead to the division and annihilation of the Union:

       I considered it [the Missouri Compromise] at once as the knell of the Union.  it [sic] is hushed indeed for the moment. but this is a reprieve only, not a final sentence.  a [sic] geographical line, coinciding with a marked principle, moral and political, once conceived and held up to the angry passions of men, will never be obliterated; and every new irritation will mark it deeper and deeper.

. . . . . . .

       I regret that I am now to die in the belief that the useless sacrifice of themselves, by the generation of $76.  to [sic] acquire self government and happiness to their country, is to be thrown away by the unwise and unworthy passions of their sons, and that my only consolation is to be that I not live to weep over it.

       [added 11/6/2020]