The Greens in Tübingen want to determine the future candidate for the mayoral election in autumn 2022 by primary election.
The general meeting on Wednesday evening accepted a proposal from the city council with a large majority.
That means: In April, the members of the city association can decide who will run for the Greens in autumn 2022 for the OB post in the university city.
A nomination event like in the last two elections, when Boris Palmer was the only candidate, will therefore not take place.
In the battle for the town hall, Palmer must now expect competition from within the party.
Palmer: "I'll think about it in peace"
The application phase lasts until February 28th, and the candidates are expected to present themselves on a podium in March.
In the invitation to the meeting, the board had written: "It cannot be dismissed out of hand that the line of dispute in the city on the question of the OB election does not currently go along a party line, but right through us."
Incumbent Palmer did not want to comment on Wednesday.
He won't say anything more about it this week.
"I'll think about it in peace," said Palmer of the German press agency dpa.
Because of numerous provocative remarks, the Greens have long been at odds with Palmer.
The Greens in Tübingen are also divided.
A party convention of the Greens in Baden-Württeberg decided at the beginning of May to initiate party regulatory proceedings against Palmer.
The reason for this decision was a Facebook post by Palmer about the former German national soccer player Dennis Aogo, in which the mayor uses the so-called N-word.
This term is used today to describe a racist term used in Germany for black people.
The OB asserted that his statement was meant ironically.