The comparative ease with which authoritarian groups have come to power in nations where large parties stood pledged to defend the democratic order to the bitter end has become one of the most disturbing elements in modern world politics. Such developments have brought into question the validity of accepted liberal-democratic norms governing the behavior of responsible leaders, both in the domestic opposition to the authoritarian regime and in foreign governments whose security arrangements are adversely affected by the suppression of free institutions. Basically, these traditional norms have implied non-interference with constitutional political processes and acceptance of their consequences. On June 23, 1933, Hitler outlawed the German Social Democratic Party (SPD), which for over four decades, until 1932, had been the largest German party and, since the founding of the Weimar Republic iri 1918, the principal advocate and defender of the democratic system and a peaceful foreign policy. In considering the actions of its leadership from the accession of Hitler to the outlawing of the party, this article seeks to contribute to a re-examination of these accepted norms, particularly insofar as they concern the behavior of a liberal-democratic mass party faced with a government seeking total power.