Supreme Court nominee Elena Kagan’s undergraduate thesis at Princeton University in 1981 was mostly a clinical analysis of the socialist movement in the United States, but in her conclusion she expressed disappointment that “labor radicalism” had failed to gain political prominence. Kagan, in her 130-page thesis, titled “To the Final Conflict: Socialism in New York City, 1900-1933,” sought to explain “why the growing and confident American socialist movement of the Progressive Era suddenly fell apart.” Kagan’s thesis, in the end, was that infighting ultimately did in the movement. “Through its own internal feuding, then, the [Socialist Party] exhausted itself forever...