Nytimes.com | By Ben Hubbard

A raft of local election victories by rivals of President Recep Tayyip Erdogan’s governing party could serve as a check on his power.

Last May, President Recep Tayyip Erdogan of Turkey handily secured another term as head of state, shattering the morale of the political opposition and raising fears among his critics that his hold on the government would enable him to further edge Turkey toward autocracy.

This weekend, the opposition struck back.

Mr. Erdogan’s opponents secured a surprising string of victories in local elections across Turkey on Sunday, increasing the number of the country’s cities under their control and further ensconcing them in most of the major metropolises.

Those opposition victories could serve as a check on Mr. Erdogan’s power at home, analysts said, while enabling rising opposition stars to wield the large budgets of major cities to build their profiles before the next presidential election, expected in 2028.

Turkey’s largest opposition party, the Republican People’s Party, won 37.8 percent of the vote, its highest share since 1977, according to preliminary results from the state-run news agency Anadolu. Mr. Erdogan’s Justice and Development Party won 35.5 percent, the agency reported, its worst showing in local elections since the party was founded more than 20 years ago.

The results were a blow to Mr. Erdogan, 70, who has been Turkey’s predominant politician for more than two decades. He has used his power as prime minister and then president to expand the role of Islam in public life and to build Turkey’s status as an economic and military player, sometimes in ways that have exasperated the United States and Turkey’s other NATO allies.

Mr. Erdogan’s critics accuse him of pushing the country toward one-man rule by cowing the news media and co-opting government institutions to serve his party’s interests. His defenders deny that he is an aspiring autocrat, pointing to his long history of success in elections that are widely regarded as free.

But the performance of Mr. Erdogan’s party on Sunday showed that many voters were unhappy, analysts said, particularly with his stewardship of the economy. A yearslong cost of living crisis has weakened the national currency, and sky high inflation has eaten away at the value of Turks’ paychecks and savings accounts.

For years, Mr. Erdogan insisted on lowering interest rates to stimulate growth, even when inflation soared above 80 percent in late 2022.

“Many government voters were disillusioned by the fact that they kept voting for Erdogan but didn’t experience any kind of real improvement in their living standards,” said Berk Esen, an associate professor of political science at Sabanci University in Istanbul.

That apparently caused some supporters of Mr. Erdogan’s party to stay home, contributing to opposition wins that Professor Esen called “really phenomenal.”

Turnout was 78 percent, down from 87 percent during the presidential and parliamentary elections last May, according to the Turkish Supreme Election Council.

And yet, the Republican People’s Party increased the number of cities it runs to 35, from 21, out of a total of 81. The party’s mayors now control six of the country’s 10 largest cities, including the top five: Istanbul, Ankara, Izmir, Bursa and Antalya.

According to the preliminary results, Mr. Erdogan’s party took one major city from the opposition, Hatay, which was heavily damaged by powerful earthquakes in February 2023 that killed more than 53,000 people.

Official results are expected from the election council in the coming days.

Addressing a crowd gathered outside his party’s headquarters in Ankara early Monday, Mr. Erdogan acknowledged the losses, calling them “a turning point” that required reflection.

“The ballot boxes are closed, the nation had its final say, made its decision,” he said. “We will examine the reasons for this setback.”

In the prelude to last year’s presidential election, Mr. Erdogan repeatedly tapped the Treasury to insulate low-income voters from economic distress, spending generously on social aid and repeatedly raising the minimum wage. But after winning the election, he changed course and appointed an economic team whom he empowered to raise interest rates to try to right the economy.

Inflation, however, has remained high, reaching 67 percent in February, according to the government. Some outside economists say the real rate is even higher.

The economic squeeze meant that before this weekend’s elections, Mr. Erdogan had “run out of artillery” and could no longer rely on the public purse to protect voters’ wallets, said Selva Demiralp, a professor of economics at Koc University in Istanbul.

“The victory of the opposition is a delayed response to the economic crisis,” she said.

Despite his party’s losses, Mr. Erdogan will most likely stick with more orthodox economic policies, hoping they will pay off in the long run, she said.

Mr. Erdogan’s re-election last year, despite Turkey’s economic troubles and accusations that his government had failed to respond swiftly after the February 2023 earthquakes, battered the mood of his opponents. A six-party coalition that had come together to try to unseat him fell apart, and a young challenger ousted the opposition’s failed presidential candidate as the leader of the largest opposition party.

But Sunday’s victories will most likely reinvigorate opposition voters and secure their leaders’ platforms to shape policy.

In the capital, Ankara, Mansur Yavas, the incumbent opposition mayor, defeated a challenger from Mr. Erdogan’s party by 28.7 percentage points.

In Istanbul, Mayor Ekrem Imamoglu defended his seat from a challenger that Mr. Erdogan and multiple ministers in his government had campaigned for, winning by 11.5 percentage points.

The loss in Istanbul was a particularly tough blow to Mr. Erdogan, given the vast budget, the large number of jobs its city hall controls and Mr. Erdogan’s personal ties to the city. He not only grew up there but also propelled his own political career forward by winning an upset election to become the city’s mayor in 1994.

The victory by Mr. Imamoglu, 52, was his third against candidates backed by Mr. Erdogan, leading many Turks to view him as a potential contender for the presidency.

“Those who do not understand the nation’s message will eventually lose,” Mr. Imamoglu told supporters outside Istanbul’s city hall early Monday.

His campaign centered on economic concerns and positive messaging in a way that resonated with voters, said Tugce Ercetin, an assistant professor of political science at Istanbul Bilgi University.

“Voters are punishing the actors they see as responsible for the economy,” she said.

When the next election will take place is an open question.

Mr. Erdogan is in the second of two presidential terms allowed by the Constitution, with a mandate until 2028. Weeks before Sunday’s vote, he said it would be his “last election.”

But some Turks think he might seek a legal avenue to remain in office, either by pressing Parliament to call for early elections, which would allow him to run again, or by amending the Constitution to permit another term.

Given the opposition’s strong showing on Sunday, its leaders could also decide to push for early elections, in hopes that they can use the ballot box to unseat Mr. Erdogan while he is perceived to be vulnerable.