 From 1896, David was a member of the "Landtag" of Hesse and after 1903 a member of the Reichstag for the SPD.He was one of the leading politicians of the "Majority" SPD when the party split during the First World War and was instrumental in framing his party's policy stand on the war.In October 1918, when the SPD became part of the Imperial government for the first time under the new chancellor Max von Baden, David became Under Secretary at the Foreign Office.