Däumig was a member of the French Foreign Legion, joining the Social Democratic Party of Germany before the first world war and became a journalist on Vorwärts in 1911. He opposed the war, and in 1917 he helped to found the USPD and became the Chief Editor of Die Freiheit from 1917-1918.
Däumig was amongst the delegates to the 2nd World Congress of the Comintern with three other members of the USPD, supporting the 21 conditions for admittance and defending them at the Halle congress of the USPD. After the USPD split and the left wing joined the KPD, Däumig became co-chairman with Paul Levi, resigning alongside him in 1921.
- Broue, P. The German Revolution: 1917-1923, pg. 487.