Two Turkish opinion polls on Wednesday showed a narrow majority of Turks, between 51-52 percent, would vote 'yes' in Sunday's referendum on changing the constitution to create an executive presidency.
Voters in Turkey will go to the polls on April 16 to decide whether to give Erdogan sweeping new powers. Voting by Turks abroad began as early as late March and will run until Sunday.
A survey by pollsters ANAR put the 'yes' vote on 52 percent. Its poll was conducted face-to-face with more than 4,000 people on April 5-10 in 26 provinces.
The number of undecided voters has fallen to 8 percent, ANAR said, adding that after distribution of these voters, there was a two percentage point rise in the 'yes' vote compared with its survey at the start of March.
The results only apply to voters in Turkey, with the level of 'yes' support among voters abroad expected to raise the 'yes' vote slightly, ANAR said in a statement shared on Twitter by its general manager Ibrahim Uslu.
Erdogan said on Tuesday Turks living overseas had turned out in greater numbers to vote, a development that pollsters say could benefit him.
The referendum campaign has damaged Turkey's ties with some European allies. Erdogan has said the banning on security grounds of some rallies by Turkish ministers in the Netherlands and Germany reflects "Nazi-like" tactics in those countries.
The Konsensus polling company put the 'yes' vote on 51.2 percent after the distribution of undecided voters. It conducted its survey face-to-face with 2,000 people on April 2-8 in 41 provinces.
