ANKARA (Reuters) - There are only two options on the ballot – “yes” or “no” – but tens of millions of Turks will cast their votes in a referendum on Sunday with a myriad of motives.

Fisherman Cengiz Topcu, 57, who says he will vote 'No' in the referendum, poses in his boat in Rize on the Black Sea coast, Turkey, April 5, 2017. REUTERS/Umit Bektas

The referendum could bring about the biggest change to Turkey’s system of governance since the founding of the modern republic almost a century ago, replacing its parliamentary system with an executive presidency.

The question on the ballot paper may be about the constitution, but looming large is the figure of President Tayyip Erdogan, who could win sweeping powers and stay in office until 2029 if the changes are approved.

Polls show a close race, with a slight lead for “yes”. But the vote may yield surprises.

“I’m a patriot,” said Cengiz Topcu, 57, a fisherman in Rize on the Black Sea coast, Erdogan’s ancestral home town where his supporters are among the most fervent. Topcu is voting “no”.

“In the past, Erdogan was a good man but then he changed for the worse. I want a democracy: not the rule of one man,” he told Reuters in his boat.

The proposed changes, Erdogan and his supporters say, will make Turkey stronger at a time when the country faces security threats from both Islamist and Kurdish militants.

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Violence has flared in the largely Kurdish southeast since the collapse of a ceasefire between the state and the outlawed Kurdistan Workers Party (PKK) in 2015, and parts of the region have long been strongholds of opposition to Erdogan.

But Hikmet Gunduz, 52, a street vendor in the main regional city of Diyarbakir, hopes his “yes” vote will help bring peace.

“I like President Erdogan’s character. He is a bit angry and a bit authoritarian but his heart is full of love.”

FREEDOMS

Erdogan, arguably modern Turkey’s most popular but divisive politician, has long cast himself as the champion of ordinary, pious Turks exploited by a secular elite.

Although a majority Muslim country, Turkey is officially secular and the headscarf was long banned in the civil service and in universities until Erdogan’s Islamist-rooted AK Party overturned that restriction.

Aynur Sullu, a 49-year-old hotel owner in the Aegean coastal city of Izmir, a bastion of the secularist opposition, said she planned to vote “yes”, dismissing suggestions that Erdogan’s Islamist ideals were encroaching on people’s private lives.

“Anyone can drink raki or swim with a bikini freely,” she said, referring to the alcoholic drink favoured by Mustafa Kemal Ataturk, the founder of the modern secular republic. “Also, now women with headscarves have freedom.”

Businesswoman Dilsat Gulsevim Arinc, however, said Erdogan was acting like a sultan and hoped her “no” vote would help teach him a “useful lesson”.

“He is too authoritarian,” said the 68-year-old cafe owner in Cesme, an Aegean resort town. “If things go on like this, I think Turkey will be finished in the next 10 years.”