FILE PHOTO: Ekrem Imamoglu , Mayor of Istanbul metropolitan municipality. AFP
Ekrem Imamoglu has turned into one of Erdogan's most outspoken and openly ambitious rivals since beating the president's ally in Istanbul's 2019 mayoral race.
The 52-year-old was initially stripped of his narrow victory and forced into a controversial rerun that he won by a massive margin.
His success in Erdogan's native city shattered the powerful president's aura of invincibility and turned Imamoglu into a hero for the ruling party's secular and liberal foes.
But his overt political ambitions and strong poll ratings have made him into a hate figure for both Erdogan and his Islamic-rooted AKP.
He was officially barred from politics after being convicted in December of "insulting a public official" and sentenced to nearly three years in jail.
Imamoglu appealed and can still serve as mayor.
But the possibility of a higher court upholding the sentence effectively ruled him out of running against Erdogan in last month's general election.
The opposition ultimately rallied around Kemal Kilicdaroglu -- a bookish 74-year-old leader of Imamoglu's CHP.
Kilicdaroglu failed to capitalise on Turkey's worst economic crisis in a generation and lost by four points in a May 28 runoff that extended Erdogan's two-decade rule until 2028.
The CHP's poor performance in accompanying parliamentary elections has added to pressure for Kilicdaroglu to make way for a younger generation of leaders such as Imamoglu.
The new charges against the mayor come with both sides turning their focus on March 2024 municipal elections in which Erdogan will try to seize back control of Istanbul and other major cities.
The case stems from Imamoglu's time as head of Istanbul's Beylikduzu district in 2015.
The indictment accuses Imamoglu and six others of "rigging" a contract in which the public allegedly suffered losses of 250,000 liras (worth $90,000 at the time).
He could be sentenced to between three and seven years in prison -- and banned from politics for a second time.
Imamoglu has rejected all charges and pointed out that an earlier investigation into the contract apportioned no blame.
He did not appear in court Thursday but has previously accused Erdogan of using the courts as a bludgeon against his political opponents.
"This case is a political conspiracy," CHP's deputy parliament group chairman Gokhan Gunaydin said in a statement. "This case will explode in the hands of those who filed it."
'Everything will be good'
A review of the 2015 tender was opened by Erdogan's hawkish former interior minister around the time when Imamoglu was being mentioned as a possible presidential candidate last year.
Turkish trials tend to run over many months and the next hearing will not take place until November 30.
But it adds a new layer of complications for both Imamoglu and the opposition as it tries to chink away into Erdogan's dominance over much of Turkey's social and political life.
The trial opened one day after Imamoglu held two hours of talks with Kilicdaroglu in Ankara in which he reportedly tried to convince the opposition leader to make way for "change".
Kilicdaroglu has refused.
The opposition leader argues that Imamoglu should keep serving as mayor to avoid seeing Turkey's biggest city fall back into Erdogan's hands.
BBC Turkce reported that Imamoglu expressed concern that the opposition may perform poorly across the nation should Kilicdaroglu hold on to his post for another year.
Imamoglu has remained tight-lipped about the talks' outcome.
"Everything will be good," he Imamoglu told reporters on his return to Istanbul.