Turks are heading to the ballot boxes in a local election that could see President Tayyip Erdogan's AK Party losing control of the capital Ankara, and even Istanbul, according to polls.
Erdogan has described the vote as a matter of survival for the country.
Turkey's economy has been declining following a currency crisis last year, where the lira lost more than 30 percent of its value. It has forced prices up, making the cost of living more difficult for many.
Erdogan has blamed the country's economic woes on attacks by the West.
“The aim behind the increasing attacks toward our country ahead of the elections is to block the road of the big, strong Turkey,” Erdogan said on Saturday.
The President has also pointed the finger at interest rates and said if the central bank lowers them, price pressures will come down too and that Turkey would overcome its troubles following Sunday’s vote.
Erdogan has dominated Turkish politics for more than 16 years, largely down to strong economic growth, but a defeat in Ankara or Istanbul would bring an end to the AK Paty's two-decade rule.
The main opposition Republican People’s Party (CHP) and Iyi (Good) Party formed an electoral alliance to rival the AKP and its nationalist MHP partners.
The pro-Kurdish opposition Peoples Democratic Party (HDP), which Erdogan has accused of links to Kurdish militants, which it denies, has not made an official alliance and is not fielding candidates for mayor in Istanbul or Ankara.
Erdogan has waned at rallies that if the opposition candidate wins in Ankara, residents would “pay a price” and accused his rivals of terrorist supporters aiming to ruin Turkey.
His opponents, however, have denied the accusations and said Erdogan is responsible for leading Turkey to its current state.
“What matter of survival? We’re electing mayors. What does this have anything to do with the country’s survival?” Kemal Kilicdaroglu, head of the CHP, told a rally in Eskisehir.
With reference to Erdogan, Kilicdaroglu said: “If there is a survival issue in Turkey, it’s because of you.”