With Democrats facing tough prospects in the midterm elections, will they also have to worry about primary challenges from their left flank? The path of Sanders' former staffers reflects the split in his movement, and the some are already galvanizing for the 2018 elections — and setting their sights on their own. The more radical strain, which led hundreds of Sanders delegates to walk out of the Democratic National Convention in protest last summer, is still present on the left and emboldened by the loss of Hillary Clinton and their belief that "Bernie would have won." A handful of groups...