Bavaria's governing conservative party has slumped to its worst state election showing in 54 years and lost its long-standing monopoly on power — a humiliating setback for a key ally of German Chancellor Angela Merkel.

Angela Merkel AP PHOTO

The conservative Christian Social Union, or CSU, won only 43.4 percent of the Sept. 28 vote, down from 60.7 percent five years ago, final results showed.

That left the CSU needing a coalition partner to run Bavaria, where it has held an absolute majority in the state Parliament for 46 years. It was the conservatives' worst result since 1954, when the party won just 38 percent of the vote.

The CSU — the Bavaria-only sister party to Merkel's Christian Democratic Union — has run the prosperous southern state since 1957.

Bavaria traditionally is an important source of votes for Merkel's conservative bloc in national elections.