Actually slavery was on it's way out because it was economically unviable and the the South slave owners had big problems with trying to grow on the land they had. . .then Andrew Jackson came along, committed the first official Trail Of Tears and sold the prime southern farm land that used to belong to the Indians to the slave owners which revitalized the the South and slave industry . .and that was all before Andrew became president. . .
Let's be honest - JFK and Truman(kind of, sort of) were outliers within the democrat party. Reagan was the first to openly admit that the democrat party wasn't the party he thought it was.