ISTANBUL — Turkey’s opposition has begun restaging an electoral battle for control of Istanbul after its candidate’s historic victory as Istanbul mayor was voided, and the ruling party has started a public relations push to explain the contentious nullification, which has hit the country's financial markets.

The Supreme Electoral Council on Monday stunned the country when it scrapped the result of the March 31 mayoral election and stripped the winner, Ekrem Imamoglu, of his mandate to lead Istanbul. The council cited irregularities in the appointment of some polling station officials in its extraordinary decision — the first time an election in a major Turkish city has been overturned.

The decision has hurtled Turkey into unmapped political terrain. While its record on democratic and human rights has been tarnished since the collapse of a peace process with Kurdish militants in 2015 and a failed military coup in 2016, it has continued to hold elections in which the ruling Justice and Development Party’s (AKP) successive victories were largely unquestioned. 

But President Recep Tayyip Erdogan’s public entreaty for a new vote to be held after his party refused to concede defeat has worried some that the ballot box may no longer be sacrosanct in Turkey.