Turkey is “on the brink of great danger”.

That was the warning from Ekrem Imamoglu, the jailed chief political rival to the country’s president, Recep Tayyip Erdogan, as the potentially fateful day of Monday September 15 loomed.

The day could see a court rule on the legitimacy of the 2023 congress held by Istanbul mayor Imamoglu’s party, the main opposition Republican People’s Party’s (CHP). If the judgement goes against the CHP over claimed irregularities, it could strip party leader Ozgur Ozel of his position.

Such an outcome would be seen by critics of the Erdogan regime as a major step to dismantling what remains in Turkey of meaningful democracy and opposition – though the CHP and Ozel have long come under fire for not being meaningful enough in the face of a powerful operator like Erdogan.

On September 14, tens of thousands protested in the capital Ankara against the court case that follows the arresting and detaining of hundreds of CHP members, including 17 mayors, over an alleged sprawling “octopus-like” network of corruption.

On social media, Imamoglu, who says he faces a range of trumped-up corruption charges in an effort by the regime to remove him from politics, said in a statement that “we are moving down a path where elections and the votes cast will lose their meaning”.

On September 12, Imamoglu was brought to court on charges pressed over the "forgery of an official document".

Authorities accuse him of forging papers related to establishing the legitimacy of his university degree. Imamoglu, jailed since mid-March after a dawn police raid on his home, is the CHP’s presidential candidate. Turkish law requires presidential candidates to hold at least an undergraduate degree.

The hearing took place in a courtroom within Marmara Prison Complex in Silivri, located on the outskirts of Istanbul. 

There was applause as Imamoglu entered the courtroom.

CHP leader Ozel arrived chanting the party's slogan, "Rights, law, justice", bianet reported.

It further reported that Imamoglu criticised the timing of the trial, referring to symbolic parallels with Turkey’s past: “The indictment was written by someone who knows I will defeat him in the next election. The very existence of this case is disgraceful. Today is September 12. This date evokes memories of military coups in the Turkish public’s collective memory. Be it military, civilian, political, or backed by the government or religious groups nurtured by the government, any kind of coup should be condemned. I strongly denounce all those who have staged, applauded, supported, or served as instruments for coups.”

He continued: “I hope our country will no longer face such interventions. But unfortunately, I must stress that we are currently going through a coup-like process. They are bankrupting hope in this country—but I won’t let them. I’m so free in my 12-square-metre cell that it would make those in their palaces burst with envy.”

Imamoglu requested that his detained lawyer Mehmet Pehlivan, held at Corlu Prison, be allowed to represent him. The judge approved the request. Pehlivan reportedly joined the hearing via the judicial video system.

In Ankara at the protest, live footage showed crowds chanting for Erdogan’s resignation while waving Turkish flags and party banners.

Ozel, accusing the government of trying to cling to power, called for a snap general election. “This case is political. The accusations are slander. Our comrades are innocent. What’s being done is a coup – a coup against the future president, against the future government. We will resist, we will resist, we will resist,” he said in his address to the crowd, as reported by Reuters.

In a message from Imamoglu read out to the crowd, clearly taking aim at Erdogan, Turkey’s leader of 22 years, Imamoglu said: “The era of ‘I’ in this country will end, and the era of ‘we’ will begin. One person will lose, and everyone else will win.”

The crowd applauded and chanted “President Imamoglu”.

Turkey’s Sozcu daily reported on September 12 that CHP youth groups, preparing for potential unrest, have stocked thousands of N95 gas masks, along with pasta, biscuits and lemons as remedies for tear gas.

Asked what a court ruling against the CHP congress could mean, Berk Esen, a political analyst at Sabanci University, told Reuters: “If such a judicial coup against the main opposition takes place, that would be the collapse of the multi-party system in Turkey.”

CHP vice president Murat Bakan told AFP: "What they're trying to create is an opposition in name only, that will not have any impact on election results like in Russia or Belarus."