Union (and the liberal democracy it represented) and emancipation were not, after all, mutually exclusive goals. Unless the Union was restored, there… - Allen C. Guelzo

[T]he attention span for political affairs in a democracy is a limited one. The fundamental genius of a liberal democracy lies in how it restrains government and permits its citizens to pursue their own interests without unnecessary molestation. So when we must address political or national issues—whether it’s “On to Richmond” or “54-40 or Fight”—we want problems addressed swiftly, so that we can turn back to our private concerns. When that doesn’t happen, we turn back to the private concerns anyway, and the problems and their solutions are left to fester or find their own solutions.

Slaves who ran away in Pennsylvania to join Sir William Howe's occupation of Philadelphia or who ran away in Virginia to join Lord Dumore's "Ethiopian Regiment" found themselves dumped by their erstwhile allies in Nova Scotia or sold back into slavery in the Bahamas.

The attempt by eleven southern—and slaveholding—states to secede from the Union in the winter and spring of 1860-61 presented the United States with the greatest internal political challenge it had ever faced. Because the Constitution had created a federal Union, secession (which broke the ties of Union) was a dagger at the heart of the American polity. The fact that this secession was motivated by Southerners' determination to protect their investment in human slavery added a cruel twist of the blade. Not only did secession fracture the Union, it did so on behalf of a practice which obliterated the fundamental natural right to liberty, which the federal Constitution was supposed to protect.