[3] In 1907 he took part with the writers Hermann Hesse, with whom he was friends, and Ludwig Thoma in the founding of the political-literary magazine März ("March"), which was initially published by Albert Langen.

Haußmann, who was committed to Franco-German reconciliation following the 1870–1871 Franco-Prussian War, provided the writer Anatole France and Jean Jaurès, a leading French social democrat, with the opportunity to contribute to März.

Prior to the outbreak of World War I, he made intensive efforts to establish contacts with French deputies at meetings in Bern and in Basel in order to reduce tensions.

With the transition to the first post-monarchical government, Haußmann gave up his post, although the new chancellor, Friedrich Ebert, would have liked to include him in his cabinet.

In early 1919 Haußmann was elected as a DDP delegate to the Weimar National Assembly, the body that drafted a new constitution for Germany and acted as its interim parliament.

He served as vice president of its Presidium and chaired the "Committee for the Preliminary Consultation of the Draft Constitution of the German Reich".