Christian Social Union of Bavaria

The CSU has led the Bavarian state government since it came into existence in 1946, save from 1954 to 1957 when the SPD formed a state government in coalition with the Bavaria Party and the state branches of the GB/BHE and FDP.

Initially, the separatist Bavaria Party (BP) successfully competed for the same electorate as the CSU, as both parties saw and presented themselves as successors to the BVP. The CSU was ultimately able to win this power struggle for itself. Among other things, the BP was involved in the "casino affair" under dubious circumstances by the CSU at the end of the 1950s and lost considerable prestige and votes. In the 1966 state election, the BP finally left the state parliament.

Franz Josef Strauß (1915–1988) had left behind the strongest legacy as a leader of the party, having led the party from 1961 until his death in 1988. His political career in the federal cabinet was unique in that he had served in four ministerial posts in the years between 1953 and 1969. From 1978 until his death in 1988, Strauß served as the Minister-President of Bavaria. Strauß was the first leader of the CSU to be a candidate for the German chancellery in 1980. In the 1980 federal election, Strauß ran against the incumbent Helmut Schmidt of the Social Democratic Party of Germany (SPD) but lost thereafter as the SPD and the Free Democratic Party (FDP) managed to secure an absolute majority together, forming a social-liberal coalition.

Before the 2008 elections in Bavaria, the CSU perennially achieved absolute majorities at the state level by itself. This level of dominance is unique among Germany's 16 states. Edmund Stoiber took over the CSU leadership in 1999. He ran for Chancellor of Germany in 2002, but his preferred CDU/CSU–FDP coalition lost against the SPD candidate Gerhard Schröder's SPD–Green alliance.

In the 2003 Bavarian state election, the CSU won 60.7% of the vote and 124 of 180 seats in the state parliament. This was the first time any party had won a two-thirds majority in a German state parliament. The Economist later suggested that this exceptional result was due to a backlash against Schröder's government in Berlin. The CSU's popularity declined in subsequent years. Stoiber stepped down from the posts of Minister-President and CSU chairman in September 2007. A year later, the CSU lost its majority in the 2008 Bavarian state election, with its vote share dropping from 60.7% to 43.4%. The CSU remained in power by forming a coalition with the FDP. In the 2009 general election, the CSU received only 42.5% of the vote in Bavaria in the 2009 election, which by then constituted its weakest showing in the party's history.

The CSU made gains in the 2013 Bavarian state election and the 2013 federal election, which were held a week apart in September 2013. The CSU regained their majority in the Bavarian Landtag and remained in government in Berlin. They had three ministers in the Fourth Merkel cabinet, namely Horst Seehofer (Minister of the Interior, Building and Community), Andreas Scheuer (Minister of Transport and Digital Infrastructure) and Gerd Müller (Minister for Economic Cooperation and Development).

The 2018 Bavarian state election yielded the worst result for the CSU in the state elections (top candidate Markus Söder) since 1950 with 37.2% of votes, a decline of over ten percentage points compared to the last result in 2013. After that, the CSU had to form a new coalition government with the minor partner Free Voters of Bavaria.

The 2021 German federal election saw the worst election result ever for the Union. The CSU also had a weak showing with 5.2% of votes nationally and 31.7% of the total in Bavaria. In the 2023 Bavarian state election, the CSU remained on 85 seats (with 37.0% of the vote) and continued its coalition government with the Free Voters.

The CSU pledges to support small and medium enterprises, opposing tax increases on these companies. In the 2006 fiscal year, the CSU presented a budget for Bavaria that was the first state to have no new debt, achieved primarily through rigorous spending cuts by all ministries. The party also states that for a new regulation to be introduced, an old regulation must be eliminated.

The CSU differs from the CDU by being more conservative in social matters. For example, the party calls for harsher punishments for those who break the blasphemy law in Germany and is generally opposed to liberalising abortions. Because of its patriotic rhetoric, which emphasizes the "Heimat", and calls for restrictions on immigration and maintaining a "Leitkultur", the CSU has been accused of exhibiting right-wing populist tendencies and adopting rhetorical elements of the AfD.

The CSU relies on the three-tier school system and justifies it in the dispute over comprehensive schools with Bavaria's good results in the PISA study. The multi-tier school system in Bavaria is seen as flexible, since all Bavarian secondary schools enable their students to obtain an intermediate school certificate.

For a long time, the CSU supported the charging of tuition fees, but in October 2012 parts of the CSU, in particular CSU chairman Horst Seehofer, were already considering abolishing them. In April 2013, the Bavarian State Parliament decided to abolish tuition fees, with the support of some CSU members.