Turkish authorities have detained Istanbul Mayor Ekrem Imamoglu—President Tayyip Erdogan’s primary political rival—on allegations of corruption and ties to a terrorist organization. The country’s main opposition party denounced the arrest on Wednesday, calling it "a coup against our next president."

The crackdown on Imamoglu, a two-term mayor, follows months of legal action against opposition figures, a campaign widely criticized as an attempt to weaken political challengers ahead of upcoming elections. The Turkish lira plummeted by as much as 12% to a record low of 42 per U.S. dollar in response, reflecting investor fears over declining rule of law in the NATO-member nation.

Imamoglu, 54, who outperforms Erdogan in some opinion polls, was set to be announced as the official presidential candidate for the opposition Republican People’s Party (CHP) in the coming days. However, he now faces multiple investigations, including allegations of running a criminal organization, bribery, and rigging municipal tenders.

Authorities imposed temporary protest bans and closed certain city streets, yet around 100 supporters gathered outside the police station where Imamoglu was taken, chanting: "The day will come when the AKP is held accountable." Larger demonstrations were in the works, setting the stage for a potential escalation in government crackdowns, which have already led to the removal of several elected opposition mayors and the imprisonment of a nationalist party leader.

CHP leader Ozgur Ozel urged opposition unity, confirming that Imamoglu’s candidacy would proceed as planned. "This is nothing short of a coup attempt against Turkey’s next president," Ozel stated.

In a video message before his detention, Imamoglu vowed resilience, declaring he would not back down despite mounting pressure.

Turkey’s next election is scheduled for 2028, but Erdogan, having reached his two-term limit as president, must either call an early election or amend the constitution to run again. Last year, Imamoglu’s CHP delivered a major electoral blow to Erdogan’s AK Party (AKP) by winning key municipal races in Turkey’s largest cities, including Istanbul, long considered an AKP stronghold.

"Today's events reinforce that Erdogan’s personal agenda takes precedence over all else, no matter the cost," said Wolfango Piccoli, co-president at consultancy Teneo.

The Turkish government insists the judiciary operates independently and rejects claims of political interference. Meanwhile, it continues efforts to end the decades-long insurgency by the outlawed Kurdistan Workers’ Party (PKK), following a ceasefire declaration last month by the group’s jailed leader, Abdullah Ocalan.

Human Rights Watch condemned Imamoglu’s arrest as "politically motivated and baseless," demanding his immediate release.

While Erdogan’s office has not responded to allegations that the arrest is a political maneuver, the Istanbul prosecutor's office announced that 100 individuals, including journalists and business figures, are under investigation for alleged crimes tied to municipal tenders. A second probe accuses Imamoglu and six others of aiding the PKK, a group designated as a terrorist organization by Turkey and its Western allies.

Adding to Imamoglu’s troubles, Istanbul University revoked his degree a day before his arrest—a move that, if upheld, could disqualify him from running for president.

Following the news, Istanbul’s stock market dropped over 5%, and the lira experienced one of its steepest intraday declines. Economists warn that the crisis could disrupt Turkey’s monetary policy, potentially halting interest rate cuts and slowing inflation, which had fallen to 39% last month.