Understanding Pete Buttigieg's race problem within the Democratic Party

During Wednesday’s Democratic debate, the newscast displayed a graphic illustrating the contrast between Pete Buttigieg’s lead in an Iowa CNN/Des Moines Register poll and the candidate’s 0% support among black voters in the latest South Carolina Quinnipiac poll. The two states have become stand-ins for two archetypal Democratic voters: white, moderate Midwesterners and black Southerners.