The correct answer to this open question is the following.
The United States already lived in a difficult situation regarding the possibility of a big division when Abraham Lincoln became the President of the United States in 1860.
Southern governmental leaders convinced themselves that the arrival of Lincoln would make things worse for their economic and political interests. Few things were really available to try to impede secession and not confronting the country. The Dred Scott decision complicated more the differences that existed in the Democratic Party.
President Lincoln was very clear in his political decisions and the southern states' leaders were sure that the best and next step, would be secession. And those ideas were so ingrained in both sides -North and South- that really nothing else could be done at that time to impede the inevitable.
1.He believed in the manifest destiny of the u.s is the reason Thomas Jefferson believe that the united states needed to acquire the Louisiana territory,
