ISTANBUL (AP) — Millions of voters in Istanbul go back to the polls for a controversial mayoral election re-run Sunday, as President Recep Tayyip Erdogan's party tries to wrest back control of Turkey's largest city.

The high-profile vote is taking place because Turkey's top election authority ruled in favor of Erdogan's Justice and Development Party, AKP, and canceled the result of the March 31 vote for mayor of Istanbul, which had given a narrow victory to opposition candidate Ekrem Imamoglu. The decision cited a breach of laws concerning the composition of officials overseeing the vote.

The race for Istanbul is seen as a test of Erdogan's popularity amid a sharp economic downturn, rising unemployment and high food prices.