Why did support for the Social Democratic Party of Germany decline during the Weimar Republic?

Support for the Social Democratic Party of Germany (SPD) declined during the Weimar Republic due to a combination of economic crises, political instability, and shifting voter allegiances.1

Key factors contributing to this decline included:

• Economic Hardship: The party faced significant challenges following the Treaty of Versailles, which imposed unfavorable terms, and severe domestic economic problems that eroded public confidence.1
• The Great Depression: The stock market crash of 1929 triggered a worldwide depression, leading to mass unemployment and business failures. In 1930, the government coalition collapsed when the SPD and the People’s Party could not agree on funding for unemployment programs, effectively ending parliamentary democracy.23
• Political Competition: The SPD had to expend significant effort competing with the Communist Party of Germany (KPD) for the working-class vote. Meanwhile, many white-collar workers and small businessmen, disillusioned by the economic disaster, shifted their support to conservative parties and eventually the Nazi Party, which capitalized on the public's fear and resentment.12