Apparently Olaf Scholz is/was not the leader of the SPD, despite being the SPD's chancellor candidate.
In 2019, Scholz wanted to become SPD chairman. However, in a membership vote, he lost out to Saskia Esken and Norbert Walter-Borjans, who had promised to move the SPD further to the left.
Scholz has always been seen as belonging to the more conservative wing of the SPD. That made it all the more surprising when Esken and Walter-Borjans nominated him as the party's chancellor candidate in August 2020. In the end, the SPD opted for a chancellor candidate it had not wanted as party leader.
So how [un]common is this type of situation in German politics, for the chancellor candidate of a (major) party not to be its formal party leader?