You don't give a time frame. The Social Democrats (SPD) and of course the Communist Party (KPD) were on the left.
left
It is governed by the Far Left, Worker's Party. a totalitarian socialist party.
A left-wing political party; the popular party in Germany in the 1920s
The political spectrum is a line that orders political ideologies from right to left: far-right is fascism (eg nazi germany); right-wing would be capitalism (eg USA); the republican/conservative party is right-wing and the democratic/liberal party is left wing; left wing government would be socialism (eg Norway) and Leninism-Marxism (eg Cuba); far left would be communism (eg Soviet Union, Red China)
Radicals are on the extreme left of the political spectrum.
on the left
the left wing
left
The Democratic Party is one of two major contemporary political parties in the United States, along with the Republican Party. The party's socially liberal and progressive platform is largely considered center-left in the U.S Political Spectrum. The party has the lengthiest record of continuous operation in the United States, and is one of the oldest political parties in the world.
The political spectrum is where parties are placed based on their policies. For example you can have right-wing or left-wing political parties. Communism and socialism are to the far left whereas fascism and conservatism is to the far right.
The traditional model of the political spectrum defines political opinions based on a spectrum ranging from left to right. It reflects different ideologies and beliefs, with the left typically associated with progressive or liberal views, and the right associated with conservative or traditional views.
Liberals and those on the left wing are typically associated with political parties that prioritize social equality, individual rights, and progressive policies. In many countries, these may include parties such as the Democratic Party in the United States, the Labour Party in the UK, or the Social Democratic Party in Germany.