Tocqueville put it best in one of those many pre-war political commentaries most Lincoln worshipers and Claremonsters like to overlook...
"However strong a government may be, it cannot easily escape from the consequences of a principle which it has once admitted as the foundation of its constitution. The Union was formed by the voluntary agreement of the states; and these, in uniting together, have not forfeited their sovereignty, nor have they been reduced to the condition of one and the same people. If one of the states chose to withdraw its name from the contract, it would be difficult to disprove its right of doing so, and the Federal government would have no means of maintaining its claims directly, either by force or by right."