President Recep Tayyip Erdoğan’s ruling party has suffered a resounding defeat in Turkey’s local polls, dealing the strongman his most severe electoral setback since his rise to power two decades ago.

Turkey’s opposition scored decisive mayoral victories against Erdoğan’s Justice and Development party (AKP) in races across the country, including in economic powerhouses Istanbul, Ankara, Izmir, Bursa and Antalya. The AKP has not performed so poorly in local elections since Erdoğan founded the Islamist-leaning party at the turn of the millennium.

Ekrem İmamoğlu’s strong performance for the opposition Republican People’s party (CHP) in Istanbul marked a painful blow to Erdoğan, who threw his full weight behind the AKP candidate in a bid to vanquish his arch-rival and the opposition’s pre-eminent politician.

“Istanbul has delivered its message,” İmamoğlu told a large crowd of supporters who gathered in the centre of the city on Monday morning. “The era of one person’s tutelage is over.”

Residents of the country’s largest city took to the streets to celebrate the result, waving Turkish flags, honking car horns, lighting colourful flares and bursting into song and dance into the early hours.

The CHP’s strong showing came as voters lashed out at Erdoğan over a long-running inflation crisis, which has sent the price of everything from groceries to vehicles and appliances soaring in recent years.

“Turkey’s main opposition party managed to defeat the ruling alliance, delivering the biggest election defeat of Erdoğan’s career,” said Berk Esen, a professor at Istanbul’s Sabancı University, who added that it was the CHP’s best showing since the 1977 general election.

Overall the CHP captured 38 per cent of the national vote, while support for the AKP fell to 35 per cent, according to initial figures from the Anadolu state news agency. The AKP had notched up 44 per cent of the vote in the previous local race in 2019.

A conciliatory Erdoğan told his supporters in the capital Ankara that with the local election over, the government could focus on fixing the economy. He promised that his efforts to rein in inflation would pay off this year and that he would prioritise foreign policy, especially curbing Kurdish aspirations for self-rule across the border in Syria.

“We unfortunately could not get the result that we wanted, that we hoped for, in the local elections,” he said. “Under no circumstances will we disrespect our people’s decision . . . That this election chapter, which has tired our nation, our people and our economy for the last year, is closed as of today is in itself a victory."

But many saw the vote for thousands of local administrators as a referendum on Erdoğan’s authoritarian style of rule, which has included interventions in monetary policy, limits on free speech and political influence in the judiciary.

“It was a ‘no’ vote to Erdoğan especially in Istanbul and a lot of other places,” said Selim Koru, an analyst at the Ankara-based Tepav think-tank.

The loss marks a stark turnaround from the presidential election of May last year, in which Erdoğan fought off a six-party opposition alliance trying to unseat him. It also bolsters İmamoğlu’s standing as the only politician in Turkey who has repeatedly been able to take on Erdoğan — Turkey’s most important leader since Mustafa Kemal Atatürk, who founded the republic a century ago.

Aslı Aydıntaşbaş, a fellow at the Washington-based Brookings Institution, said Erdoğan “can no longer count on an opposition that is in disarray”.

İmamoğlu, 53, beat AKP candidate Murat Kurum by 12 percentage points in the Istanbul race, taking 51 per cent of the vote, according to Anadolu. That marks the highest margin of victory for an Istanbul mayor in four decades.

Erdoğan, 70, had deployed a barrage of resources to the city, holding rallies and dispatching top ministers to campaign for Kurum, as state-aligned media showered the former urbanisation minister with coverage.

İmamoğlu’s win echoes the municipal race in 2019, when he took control of Istanbul in a highly charged campaign in which Erdoğan’s party forced — and then lost — a repeat of the vote.

In Ankara, support for the opposition was even more dramatic, with incumbent mayor Mansur Yavaş declaring victory after securing 60 per cent of the vote, far ahead of AKP opponent Turgut Altınok, who took 32 per cent.

Turkish markets advanced on Monday on hopes that an economic overhaul programme that began in June will remain intact despite Erdoğan’s electoral setback. The lira rose about 1 per cent to TL32.1 to the dollar and Istanbul’s Bist 100 equities index ticked up slightly.

Beyond the country’s biggest cities, the AKP faced the loss of provinces where it has dominated for the past decade or longer, mostly in western Turkey.

The CHP wrested control of the southern city of Adıyaman, one of the areas hardest hit in the 2023 earthquake, and Kilis, a conservative province that borders Syria.

In the predominantly Kurdish south-east, the Peoples’ Equality and Democracy party won 10 provincial capitals, compared with eight in 2019. The party has faced a long-running crackdown by Erdoğan that has included the jailing of several of its mayors and its former chair, Selahattin Demirtaş.

The Islamist New Welfare party captured the religiously conservative cities of Şanlıurfa and Yozgat. The party had supported Erdoğan in last year’s general election but broke with the AKP in this vote over disagreements on trade with Israel and economic policies.

“It’s enough AKP. We are tired of the AKP because of the economic situation. Everything is so expensive,” said 59-year-old Şanlıurfa resident Ramazan Çimen, who has typically voted for the AKP but said he was now backing New Welfare. “We need a change in this country.”