Although Mueller is set to give up his job as mayor – which gives him the same powers as a state premier – he had not planned to leave politics and had put his hopes into becoming the candidate for Berlin’s Charlottenburg-Wilmersdorf seat for his centre-left Social Democrats (SPD).

But those plans encountered some unexpected turbulence when another SPD member – Sawsan Chebli, who runs the city’s civic engagement office – announced that she also wanted to run for that seat.

But, on Wednesday, SPD members in the district announced that Mueller will be their candidate. That means, if the SPD wins the seat at the federal election expected next year, Mueller would become a member of the Bundestag.

About 2,500 members participated in the non-binding vote. The final decision on the party’s candidate will come next month, but the membership poll will weigh heavily on that decision.

And there’s another wrinkle. At the last election, the Charlottenburg-Wilmersdorf seat went to the centre-right Christian Democrats, meaning Mueller, or any other SPD candidate, still has work to do.