(SPD). Joint stock companies were formed to manage the state-owned mines, salt works, smelters, water works, and electrical generation plants. Ideas about the economic common good, such as those advocated by State Secretary Hans Staudinger (SPD), also played a role in the expedited development of state-owned companies. Political system Party system The Prussian party system – made up of conservatism (German National People's Party, DNVP), political Catholicism (Centre Party), liberalism (German People's Party, DVP, and German Democratic Party, DDP), social democracy (Majority Social Democratic Party, MSPD) and socialism/communism (Independent Social Democratic Party, USPD, and Communist Party of Germany, KPD) – corresponded to that at the Reich level. The DNVP had a special affinity to the former Prussian monarchy. Among the regional parties, the German-Hanoverian Party (DHP) had some influence. The MSPD and USPD, which had split in 1917, merged in 1922 and resumed the original SPD name. (A small and politically insignificant part of the USPD continued to exist until 1931 when it merged with the Socialist Worker's Party of Germany.) The DNVP and DVP had strongholds in a few cities and in areas that were more rural and Protestant, especially east of the Elbe River. In East Prussia the DNVP received over 30% of the vote in the 1928 federal election for the Reichstag. The Centre was strong in Catholic areas such as Silesia, the Rhineland and Westphalia. The left-wing parties were important in large cities and heavily commercial non-Catholic areas. In Berlin, for example, the SPD's vote came to 34% in 1928 and the KPD's to almost 30%. The rise of the Nazi Party (NSDAP) changed the pattern, but it remained dominant in basic terms until 1932. Within Prussia there were considerable differences in support for the Republic. The majority in Berlin, the Rhineland and Westphalia were in favor of a democracy, while reservations remained in the eastern and agrarian provinces. In the March 1933 Reichstag elections, the NSDAP had above-average strength in constituencies such as East Prussia (56.5%), Frankfurt an der Oder (55.2%), Liegnitz (54%) and Schleswig-Holstein (53.2%), but was significantly weaker in Berlin (31.3%), Westphalia (34.3%) and the Rhineland (34.1%) than the Reich average (43.9%). A factor in Prussia's political stability was that the SPD, which was the strongest party during most of the Weimar Republic, was prepared until 1932 to assume government responsibility and not withdraw into an opposition role as it had at the