Southern Democrats are members of the U.S. Democratic Party who reside in the American South and they walked out of the first democrat convention in 1860 because they wanted to secede and there was much opposition!
I'm not Ms. Sue, but I hope I helped! :)
Why did Southern Democrats walk out of the Democratic Convention?
2 answers
They actually wanted a candidate who was in favor of the expansion of slavery and felt that Stephen Douglas, the nominee, was insufficiently on their side. He was not anti-slavery, but not pro-slavery enough, in essence. Read this:
http://study.com/academy/lesson/the-1860-democratic-national-convention-the-party-splits.html
http://study.com/academy/lesson/the-1860-democratic-national-convention-the-party-splits.html