Mr Erdogan is polling at 56% after almost half of the votes have been counted, Turkish broadcasters said.
He needs more than 50% of the vote for an outright victory, otherwise he will face a second round on 24 August.
Mr Erdogan, 60, says if he wins, he wants to bolster the power of the largely ceremonial post of president.He has been prime minister since 2003 and is barred from standing for that office again.
‘Show our colours’ The BBC’s Mark Lowen in the capital Ankara says turnout appears to be much lower than expected.The summer heat and holidays may have dissuaded some voters, our correspondent says.
Turkey – wedged between the turmoil of Iraq, Syria and Ukraine – is an important ally for the West, our correspondent adds, and whoever becomes head of state will hold a key geopolitical position.
Mr Erdogan’s two rivals are a little-known diplomat, Ekmeleddin Ihsanoglu, and Kurdish politician Selahattin Demirtas.
Mr Ihsanoglu, 71, is the joint candidate of the two main opposition parties in parliament, the centre-left Republican People’s Party (CHP) and the far-right Nationalist Movement Party (MHP).He served as the secretary-general of the Organization of Islamic Cooperation from 2004 to 2014.
Mr Ihsanoglu has vowed to uphold the president’s traditional role, insisting it is not up to the head of state to be involved in day-to-day running of politics.
Mr Demirtas, 41, is a leader of the left-wing People’s Democratic Party (HDP) and a well-known politician from the Kurdish minority.
He has focused his campaign on championing the cause of the oppressed, the poor, the young and the working classes.
“We cannot build our union by accusing each other. Let’s show our colours at the ballot box tomorrow with our oppressed identities and faiths,” Mr Demirtas told crowds in the city of Izmir ahead of the elections.
In his final rally in the city of Konya on Saturday, Mr Erdogan vowed to raise Turkey’s democratic standards and economic record to create a “world leader and global power”.
“There is no unattainable dream or unattainable objective for this nation,” he said.
BBC News.Sunday, August 10, 2014