 On 8 August 1929, he started as of the head of the provincial government ("Regierungspräsident") in Merseburg.Harnack was dismissed from government service after the so-called Preußenschlag by Reichskanzler (Chancellor) Franz von Papen on 20 July 1932.On 27 November 1921 he was elected to the executive committee of the "Kirchenpartei" called "Bund religiöser Sozialisten" (Federation of Religious Socialists).