Turkish Prime Minister Binali Yildirim, whose job will disappear if the yes vote wins, warmed up the crowd for Erdogan as tens of thousands of supporters flooded to the rally on the banks of the Bosphorous on Saturday afternoon.
Many, like Ahmed, could hardly contain their enthusiasm.
“I love you Recep Tayyip Erdogan!" he gushed. "I love you Binali Yildirim! Yes, government OK!”
Until now the presidency has officially been a ceremonial, neutral post.
In reality Erdogan has already changed that, dominating the ruling Justice and Development Party (AKP) and the government from his newly built presidential palace. The proposed constitutional changes would make that official, allowing him to form governments, declare states of emergency and pick some of the country’s top judges.
After decades of coalition governments, the changes will make government more efficient, the AKP argues.
“We need government to do good things for the people," Erdogan supporter Cihan said on his way into the rally. "And, on the other hand, there should be a parliament to make laws, so this should be separate and with this new system, I believe this will work. And, as the people, we will be careful if this system works or not. We will be the judge, we will choose, we will decide.”
Bitter opposition from left
Not everyone agrees.
The secular opposition Republican People’s Party, the CHP, and left-wing groups like the pro-Kurd People’s Democratic Party say the changes are a further step towards dictatorship after 15 years of increasingly authoritarian AKP rule.
Campaigning in the Istanbul’s Kadikoy district, CHP member Anil was as vehemently against Erdogan as AKP supporters are for him, accusing him of self-interest bordering on corruption.
"He wants to take rule of everything and everyone, just so as to get away with things, get away with the things he’s done with his family, with his cronies around him," he aid. "He’s not interested in ideologies, he’s not interested in the good he does for the people. He’s lying, he’s a liar. I believe he is. Yes.”
Democracy, human rights
Turks have become increasingly reluctant to express their opinions to the media over the years of Erdogan’s reigns as prime minister and president.
So many people were reluctant to comment in the bazaar at Eminonu, near the Topkapi Palace of the sultans, although some of the traders and customers were ready to do so.
Erman, a member of the Christian Armenian minority, said he had voted for the AKP twice because they initially had a more tolerant policy than secular nationalist governments. But he will not vote for the constitutional changes.
“They built new churches, new schools but I don’t think this will happen again,” he explained. “Because with one leader everything will involve him and if he says anything everybody will think it is true. But I don’t think one man will change everything. This is not credible to me.”
Another man, who refused to give his name, listed his concerns “Democracy, human rights, education,” dubbing Erdogan a dictator and a would-be sultan.
Not that that view was unanimous.
Uzgur, who has a shoe stall in an underpass by the Bosphorous, was voting yes “because I like Recep Tayyip Erdogan” and a yes vote would make the Turkish people powerful.
Erdogan’s personal popularity and his slogan of a strong Turkey are often cited by his supporters.
And European countries’ criticisms
of their president, and Dutch and German refusals to allow ministers to campaign for a yes vote in their countries, infuriate them.
“We want to show all Europe that Turkey is strong,” AKP member Imir said. “Look at Europe. Look at [German Chancellor Angela] Merkel. It’s the same system. Europe doesn’t want Turkey to have this system because they don’t want a strong Turkey.”
The campaign has been bitter on both sides and has deepened Turkey’s already profound political divisions.
Erdogan has massive popular support and can attract vast, adoring crowds at his rallies.
On Sunday, 16 April, we’ll see whether that will translate into support for his plan for a highly centralised presidential system.