ISTANBUL — In the last day before Turkey's crucial referendum on whether to expand the president's power, both "yes" and "no" campaigners addressed flag-waving supporters Saturday in Istanbul and Ankara.
At stake is the future of Turkey's political system, with supporters saying the constitutional changes will herald a period of stability and prosperity, and detractors warning the reforms could lead to an autocratic one-man rule by President Recep Tayyip Erdogan.
Opinion polls indicate a tight race, and fierce campaigning took place Saturday right up to a 6 p.m. ban.
Erdogan has long championed the idea of changing Turkey's system of government from parliamentary to presidential. He is calling on his countrymen to vote Sunday to approve 18 constitutional changes that would, among other things, abolish the office of the prime minister, handing all executive power to the president.
"The new constitution will bring stability and trust that is needed for our county to develop and grow," Erdogan told supporters Saturday in Istanbul's Tuzla district. He also appealed to voters of other parties to approve the changes so "Turkey can leap into the future."
"Is it a 'yes' for one nation? Is it a 'yes' for one flag? Is it a 'yes' for one homeland? Is it a 'yes' for one state? Yes, yes, yes!" he said.
Erdogan said the proposed reforms could help counter a series of threats, including a failed military coup last year and a string of deadly bombings, some attributed to the Islamic State group. Fighting also resumed in 2015 between security forces and Kurdish rebels in the southeast of the country.
But critics argue that Erdogan, who has been at the helm of Turkish government as prime minister or president since 2003, will simply cement his hold on power with even fewer checks and balances if the "yes" side wins.
"Turkey is at a junction. We will make our decision tomorrow. Do we want a democratic parliamentary system or do we want a one-man regime?" Kemal Kilicdaroglu, leader of the main opposition Republican People's Party, asked supporters in the capital, Ankara.
In Istanbul on Saturday, thousands of "no" supporters waving Turkish flags marched along the Bosphorus.
The opposition has complained of a lopsided campaign, with Erdogan using the full resources of the state and the governing party to dominate the airwaves and blanket the country with "yes" campaign posters. "No" campaigners say they have recorded more than 100 incidents of intimidation, beatings and arbitrary detentions.
Erdogan has painted supporters of the "no" campaign as people bent on destabilizing the nation, accusing them of siding with those blamed for the July 2016 attempted coup.
"Sunday will be a turning point in our struggle against terrorism," Erdogan said.
The referendum comes as Turkey is still under a state of emergency declared after the failed coup. Some 100,000 people, including judges, lawyers, teachers, journalists and police, have been dismissed from their jobs. More than 40,000 people, including opposition pro-Kurdish legislators, have been arrested. Hundreds of news outlets and non-governmental organizations have been shut down.
"We want peace, freedom, democracy. We will have these with a 'no' vote tomorrow," Pervin Buldan, a lawmaker from the opposition pro-Kurdish Peoples' Democratic Party, said at a rally in the predominantly Kurdish province of Diyarbakir.
Security will be high for Sunday's vote, with nearly 34,000 police deployed in Istanbul alone. The Islamic State group has called for attacks against the referendum.
On Saturday, Turkey's official Anadolu news agency said 49 people, including 41 foreigners, were detained on suspicion of planning attacks during the vote.
Suzan Fraser contributed from Ankara, Turkey.