At the first debate, Joe Biden took ownership of today's Democrats with an uncharacteristically clear proclamation: "I am the Democratic Party." With that, Biden assumed responsibility for repudiating and distancing himself from the anti-Semitism surging through his party's ranks. Anti-Semitism has been on full display among Democratic leaders and left-wing protest groups alike in recent years. Leaders of the Women's March, for example, proved so undeniably anti-Semitic that even former DNC chair Debbie Wasserman-Schultz felt compelled to distance herself. Yet those same anti-Semites—Linda Sarsour and Tamika Mallory—were featured speakers at this summer's Democratic convention. The Women's March since recruited new...