Overview
A bloc party (German: Blockpartei), sometimes called a satellite party, is a political party that is a constituent member of an electoral bloc. However, the term also has a more specific meaning, referring to non-ruling but legal political parties in a one-party state (most notably communist regimes) as auxiliary parties and members of a ruling coalition, differing such governments from pure one-party states such as Nazi Germany and the Soviet Union, although such minor parties rarely if ever constitute opposition parties or alternative sources of power. Other authoritarian regimes may also have multiple political parties which are nominally independent in order to give the appearance of political pluralism, but support or act in de facto cooperation with the government or ruling party.
Background
The concept has its roots in the Popular front idea where Marxist and non-Marxist political parties and other organisations would belong in an umbrella organisation. Following the end of World War II, elections were held in areas already under Soviet influence who would become members of the Eastern Bloc, that while giving voters a choice would be seen as a step towards a totalitarian, Communist-led regime. Bloc parties were able to retain their non-Marxist orientation, but in practice were always subordinate to the ruling Communist party, and were required to accept the Communists' “leading role" as a condition of their continued existence. All legal parties and civic organisations were required to be members of the official Communist-dominated coalition. Elections were not competitive as the composition of legislatures was generally pre-determined.
Parties only occasionally dissented from the line of the ruling party. Some parties were pre-existing, others had been newly formed, to appeal to specific sectors of society.
From Wikipedia (CC BY-SA 4.0).