"STABILITY OR CRISIS"
While constitutionally required to stay above party politics, Erdogan has held frequent rallies during what has been a confrontational election campaign, joining Prime Minister Ahmet Davutoglu in attacking opposition parties.
The two have portrayed the election as a choice between a "new Turkey" or a return to a history marked by short-lived coalition governments, economic instability and military coups.
"Either the stability of the last 12 years will continue, or there will be the crisis scenario of those who want to take Turkey back to the chaos and crisis atmosphere of the 1990s," Davutoglu told a rally in the southern city of Antalya.
It is a message which resonates with religiously conservative voters in Turkey's Anatolian heartland, including the city of Konya, an AKP stronghold where Davutoglu was set to vote.
"I voted for the AK Party and for Davutoglu. He's an honest man, a good Muslim, he prays five times a day, and he's from Konya like us," 59-year-old Ekrem Bal, twirling prayer beads outside a polling station, said.
Ratcheting up tension ahead of the vote, HDP leader Selahattin Demirtas called for Erdogan to apologize for his muted response to Friday's bombing of an HDP rally in Diyarbakir, which killed two and wounded more than 200.
Security was tightened after the attack and some 9,000 police and gendarmerie officers were assigned for duty in Diyarbakir on Sunday.
Erdogan late on Friday expressed his condolences for victims of the attack, calling it a "provocation".
While he says he is equally distant from all parties, HDP leaders have accused Erdogan of whipping up sentiment against them and party deputy Idris Baluken said he and the AKP bore responsibility for Friday's attack.
"The source of the violence is the AKP, the president. For two months, we have been warning that the rhetoric would result in just this, including in our talks with the government," Baluken told Reuters.