Former Vice President Joe Biden won the Mississippi primary on Tuesday, the latest in his string of victories in the deep south, where black voters have turned out in big numbers to support his campaign. News outlets called the victory for Biden over Sen. Bernie Sanders (I-Vt.) as soon as polls closed. Biden’s final margin of victory is not known yet, but polls showed him up by 50 points heading into Election Day, so he’ll likely win a strong majority of the 36 delegates up for grabs. Sanders cancelled a planned event in Mississippi last week, deciding instead that his...