Turkish President Recep Tayyip Erdogan is behind main rival Kemal Kilicdaroglu by more than five percentage points ahead of Sunday's presidential election, a survey by the pollster Konda showed on Thursday.
Mr Erdogan was predicted to win 43.7 per cent of the vote and Mr Kilicdaroglu 49.3 per cent, leaving him short of the majority needed to win in the first round, suggesting the election will go to a run-off on May 28.
The findings reinforced the impression that Mr Erdogan faces the biggest challenge of his two-decade rule in the vote. They were largely in line with some other polls that put Mr Kilicdaroglu, candidate of the main opposition alliance, ahead.
Mr Kilicdaroglu is seen as the symbol of a potential new future that threatens the President as he is representing Turkey's six-party opposition alliance.
The survey, carried out May 6 and May 7, put support for the other two candidates at 4.8 per cent for Sinan Ogan and 2.2 per cent for Muharrem Ince. Shortly after polling was released, Mr Ince withdrew from the race.
Konda said the majority of voters were leaning towards voting for Mr Kilicdaroglu, leader of the main opposition Republican People's Party (CHP).
The elections will take place three months after an earthquake that killed more than 50,000 in Turkey and left millions homeless.
Konda, which publicly releases only one poll ahead of votes, undertook face-to-face interviews with 3,480 people across 35 provincial centres.