Here's Why The South Poses A Huge Problem For Bernie Sanders

The Clinton campaign's focus on what's beyond the first four primary and caucus states of Iowa, New Hampshire, Nevada and South Carolina is a lesson learned from the 2008 Democratic presidential primary, when President Barack Obama's team methodically built up more of an infrastructure in later states than she did. 

To undercut the perception that Clinton has a massive advantage in the Southern states that will guarantee her the nomination, Sanders' campaign has argued it could still pick up delegates in states he doesn't win.