Months of rancorous campaigning have come to an end it Turkey - less a day before voters go to the polls to decide the country’s future. At stake is the question of presidential power versus parliamentary democracy.
President Recep Tayyip Erodgan called the referendum last year, seeking to do away with the prime minister's post, limit the power of parliament and consolidate power in the presidency.
Erdogan, who came to power as prime minister in 2003, before assuming the presidency in 2014, could end up serving as president through 2029 of the "Yes” vote prevails on Sunday.
"Turkey will tomorrow make one of the most important decisions in its history," Erdogan said, as he wrapped up an exhausting nationwide campaign with a rally in the Istanbul.
Confidently predicting victory, he declared: "The polls look really good." But he urged people not to succumb to "lethargy" in voting, saying "the stronger result, the better."
Europe was inadvertently drawn into the campaign when some countries forbade Erdogan supporters from holding campaign rallies in their respective countries. An irate Erdogan likened Europe to the Nazis.
"A 'Yes' that emerges from the ballot box with the highest margin will be a lesson to the West," Erdogan said referring to his feud with the European Union.
A runaway bus
A leading figure in the 'No' camp, Republican People's Party (CHP) leader Kemal Kilicdaroglu, warned at a meeting in the Ankara region that Turkey was deciding if "we want to continue with the democratic parliamentary system or one-man rule."
He described the system proposed by Erdogan as "a bus with no brakes and whose destination is unknown."
The opposition has also cried foul over the campaign for referendum, which they say has been unfair. "Yes" posters are ubiquitous on the streets and opposition voices have largely been squeezed out of the media.
Despite some clear advantages, the campaign has not been clear sailing for Erdogan. Some heavyweight figures within the ruling Justice and Development Party (AKP) have been conspicuously silent on the new system, including former Prime Minister Ahmet Davutoglu.
Opinion polls are all over the place, leaving analysts to predict a close result, though there is some consensus that the "Yes" vote has a narrow lead.
A slew of attacks over the past year, blamed on Kurdish militants and jihadists, has made security a major issue for polling day.
Authorities in Istanbul on Friday detained five people suspected of planning an attack on Sunday, following the arrest of 19 alleged Islamist extremists in the Aegean city of Izmir earlier in the week.
More than 33,500 police officers will be on duty in Istanbul alone.
Some 55 million people are eligible to vote at more than 167,000 polling stations across the country. Polls open at 7 a.m. (0400 GMT) in the east of the country and close at 5 p.m. (1400 GMT). Voters abroad have already cast their ballots.
bik/rc (AFP, Reuters, dpa)