[11] Along with the right-liberal German People's Party (Deutsche Volkspartei, DVP), it represented political liberalism in Germany between 1918 and 1933.
After the formation of the first German state to be constituted along pluralist-democratic lines, the DDP took part as a member of varying coalitions in almost all Weimar Republic cabinets from 1919 to 1932.
Before the Reichstag elections of 1930, it united with the Volksnationale Reichsvereinigung, which was part of the national liberal Young German Order (Jungdeutscher Orden).
Theodor Barth and his supporters broke away into the Democratic Union in 1908, and maintained their independence until joining the DDP in 1918.
[17] The DDP was a member of the Scheidemann cabinet, but left in June 1919 in response to the Treaty of Versailles before returning to the coalition in October.
[18] Friedrich von Payer resigned as chair of the DDP's legislative caucus after voting in favor of the treaty.
[25] In spite its steadily dwindling size, the DDP played an important political role in the early years of the Republic.
For one, its position between the SPD and the Centre Party helped stabilize the Weimar Coalition nationwide and especially in Prussia.
In addition, members of the DDP formed an important reservoir of personnel for high positions in public administration.
This visionary idea was out of touch with the reality of rising unemployment and economic difficulties under the pressure of the Treaty of Versailles.
In July 1930, the DDP united with the People's National Reich Association (VNR) to form the German State Party, initially for the upcoming Reichstag elections.
This brought fierce conflicts within the party, as the VNR was the political arm of Artur Mahraun's national liberal Young German Order.
Hermann von Richthofen, Peter Reinhold, and others left the party after failing to convince its leadership to dissolve it.
[30][31] The DStP deputies, as opposed to the SPD, voted for the Nazi-sponsored Enabling Act, which effectively disempowered the Reichstag.
The final sentence of his speech read: "In the interest of the people and the Fatherland and in the expectation of lawful developments, we will put aside our serious misgivings and agree to the Enabling Act.
[35] Since the mandates of the DStP’s Reichstag deputies had been won by means of nominations from the Social Democratic Party, they expired in July 1933 based on a provision of the Gleichschaltung Law of 31 March 1933.
It consisted of the diplomat Franz Sperr as well as the former Weimar Reich ministers and DDP members Otto Geßler and Eduard Hamm.
Many former members of the DDP and Radical Democratic Party also found themselves forced into exile either because of their stance against the regime or their pacifist attitudes, among them Ludwig Quidde and Wilhelm Abegg.
It was also supported by executives and civil servants, industrialists mainly from the chemical and electrical industries and liberal Jews.
Otto Fischbeck, Conrad Haußmann, and Payer supported the continued existence of the Prussian state.