The Christian Democratic Union (CDU) and the Christian Social Union (CSU) are not a single party under German law; they are legally distinct entities. However, they operate as a tightly knit political alliance, commonly referred to as the “Union,” with a unique arrangement that shapes their relationship in German politics.
According to German federal electoral law, specifically the Bundeswahlgesetz (Federal Election Law), parties are recognized as separate organizations based on their registration and operational scope. The CDU and CSU maintain separate party structures, memberships, and leaderships. The CDU operates in all German states except Bavaria, while the CSU is active exclusively in Bavaria. This division stems from their historical roots: the CDU was founded in 1945 as a broad Christian democratic party across Germany, while the CSU emerged as a Bavarian-specific party with a stronger conservative and regionalist identity, reflecting Bavaria’s distinct cultural and political traditions.
What makes their relationship unique is their parliamentary cooperation. In the German Bundestag, the CDU and CSU form a single parliamentary group, known as the CDU/CSU-Fraktion. German law allows parties with shared political goals to unite in this way, as outlined in the Geschäftsordnung des Deutschen Bundestages (Rules of Procedure of the German Bundestag). This joint faction has existed since 1949, when the Federal Republic was established, and it enables them to act as a unified bloc on the federal level, pooling their votes and agreeing on a common chancellor candidate during elections. The Federal Electoral Law also stipulates that parties forming a joint parliamentary group must not compete against each other in any federal state, which is why the CDU does not field candidates in Bavaria, and the CSU does not contest elections outside Bavaria.
Despite this close alliance, the CDU and CSU remain legally independent. They have separate party charters, hold distinct party conferences, and occasionally adopt differing policy positions—most notably when the CSU pushes a more conservative line, such as on immigration or Bavarian autonomy. There have even been moments of tension, like in the 1970s when CSU leader Franz Josef Strauß proposed splitting from the CDU to pursue a more right-wing national strategy, though this never came to fruition.
So, under German law, the CDU and CSU are two separate parties, not a single entity. Their unity is a practical and political arrangement rather than a legal merger, allowing them to maintain individual identities while functioning as a cohesive force in federal politics. This setup is a quirk of Germany’s federal system, balancing regional diversity with national cooperation.