CROWDS OF PROTESTERS streamed onto the square outside Istanbul’s city hall on March 23rd to support their mayor, Ekrem Imamoglu, the Turkish opposition’s star politician. Nearly 15m voters had just confirmed Mr Imamoglu as the candidate of the Republican People’s Party (CHP) at the country’s next presidential elections, the party said. But the rally was no celebration. The man the opposition supporters had come out to cheer was behind bars.