In setback to Erdogan, opposition makes huge gains in local election

Turkey's main opposition party retained its control over key cities and made huge gains elsewhere in Sunday's local elections, in a major upset to President Recep Tayyip Erdogan, who had set his sights on retaking control of those urban areas.

With more than 90% of ballot boxes counted, incumbent Istanbul Mayor Ekrem Imamoglu, of the Republican People's Party, or CHP, was leading by a wide margin in Turkey's largest city and economic hub, according to the state-run Anadolu Agency. Mansur Yavas, the mayor of the capital, Ankara, retained his seat with a stunning 25-point difference over his challenger, the results indicated.

In all, the CHP won the municipalities of 36 of Turkey's 81 provinces, according to Anadolu, making inroads into many strongholds of Erdogan's party. It gained 37% of the votes nationwide, compared to 36% for the president's party, marking the CHP...