In 1918, he joined the DDP in Baden. In 1922, he became Minister for Teaching, and in 1924, with the surge of support to the DDP, became State President of Baden. In elections the following year, the Centre Party under Gustav Trunk regained their majority. Hellpach then ran for Reich President following the death of Friedrich Ebert, but only received 5.8% of the vote. Following a brief (1928–1930) seat in the Reichstag, Hellpach withdrew from politics.
He wrote a book Die Geopsychischen Erscheinungen: Wetter, Klima Und Landschaft In Ihrem Einfluss Auf Das Seelenleben (in 1911) (revised as Geopsyche in 1935) that is credited with being the first mention of the field of environmental psychology.