The mood among opposition supporters in Turkey’s biggest city is one of jubilation but also worry — fear that their win in Istanbul’s mayoral race could be overturned in a recount taking place after the ruling party challenged the election results.

In an unexpected setback to President Recep Tayyip Erdogan, the opposition snatched away his ruling party’s quarter-century-old stronghold of Ankara, the capital, in Turkey’s local election last Sunday. The opposition also won a tight race in Istanbul, the country’s financial and cultural capital, where Erdogan himself rose to power as mayor in 1994.

The opposition made these gains despite an election that international observers say was not fair. Turkish media covered Erdogan’s constant campaign appearances on behalf of his party but did not give remotely similar coverage to opposition candidates.