It is very much hard to answer.
It was mainly because of how the North and the South of America had different lifestyles and economy's. You would be surprised to know that the Democratic party back then supported Slavery and the republicans dint support Slavery.
Plain Answer: Because of Slavery, Way of Life and Different Economy. The Democratic Party would do anything to keep themselves supported.
Answer: I'm pretty sure it is The New Deal
Explanation: I had this question in a test and I remember I chose The New Deal and got it right
