Turkey has entered the final stretch of a historic election campaign and public opinion polls are giving President Recep Tayyip Erdogan a clear lead in his re-election bid. Yet a lack of confidence surrounding opinion research in Turkish politics may be skewing results ahead of an election that may be too close to call.

Electoral rules restrict polling in the final 10 days of a campaign to prevent such research from swaying voters, and pollsters have rushed to release data, with a handful putting Erdogan’s share of the vote above 50% — the percentage needed to win in a first-round of voting on June 24. If he falls short of half of the vote, a runoff between the top two candidates will be held on July 8.

Politicians, journalists, investors and political analysts are closely tracking the data despite most polls' failure to accurately predict outcomes in recent Turkish elections. Polling data released in the the final 10 days must include details about the organization conducting the research, the number of subjects and who is financing the research.

Turkish election polling is “wholly unreliable," said Michael Daventry, a journalist who runs the James in Turkey blog that closely monitors Turkish electoral politics. "There is no Turkish pollster who publishes public data that is reliable, because they don’t share how they gathered the data and they don’t reveal who paid for the research. Those are the two main things you would expect from any pollster.”