This is supposedly Bernie Sanders’ problem, in a nutshell:
The problem for Sanders is a demographic one. In the South, where a number of states hold primaries in February and the first half of March, Clinton still has a lock on nonwhite Democrats.
On March 1, primary voters in Alabama, Arkansas, Georgia, Oklahoma, Tennessee, Texas and Virginia — all states where Clinton is expected to come out ahead — will go to the polls. Voters in Colorado, Massachusetts, Minnesota and Sanders’ home state of Vermont will as well, and though Sanders has a chance of winning any of those states, their delegate counts pale in comparison to those in a larger state like Texas.