From 1919, Lohse was first an associate at the Schleswig-Holstein Farmers' Association, and then as of 1920 General Secretary of the Schleswig-Holsteinische Bauern- und Landarbeiterdemokratie. In 1923 he joined the Nazi Party and became on 27 March 1925 the NSDAP Gauleiter for Schleswig-Holstein. In 1924, as a member of the Völkisch-Sozialer Block list, he became the only Nazi to be elected to the city representative college (Stadtverordnetenkollegium) of Altona/Elbe.