With four well-chosen words, Vice President Biden summed up the most important ideological dividing line in the Democratic presidential primary. The comment came at the third of three fundraisers Mr. Biden held on Thursday at Los Angeles County. Usually Mr. Biden sticks to his stump speech, and keeps his schedule a bit lighter than three public events in a day. So perhaps it was the candor that comes with fatigue. Perhaps it was the intimacy that came with the unusually small event about 50...
