Turks vote for a new president and parliament on Sunday in elections that pose the biggest challenge to Tayyip Erdogan and his Islamist-rooted AK Party since they swept to power more than a decade and a half ago. The elections will also usher in a powerful new executive presidency long sought by Erdogan and backed by a small majority of Turks in a 2017 referendum. Critics say it will further erode democracy in the NATO member state and entrench one-man rule. Erdogan, the most popular but also divisive leader in modern Turkish history, moved the elections forward from November 2019, arguing the new powers would better enable him to tackle the nation's mounting economic problems - the lira has lost 20 percent against the dollar this year - and deal with Kurdish rebels in southeast Turkey and in neighbouring Iraq and Syria. But he reckoned without Muharrem Ince, the presidential candidate of the secularist Republican People's Party (CHP), whose feisty performance at campaign rallies has galvanised Turkey's long-demoralised and divided opposition. Addressing a rally in Istanbul on Saturday attended by at least one million people, and possibly many more, Ince promised to reverse what he and opposition parties see as Turkey's swing towards authoritarian rule under Erdogan. "If Erdogan wins, your phones will continue to be listened to . Fear will continue to reign . If Ince wins, the courts will be independent," said Ince, adding he would lift Turkey's state of emergency within 48 hours of being elected. Turkey has been under emergency rule - which restricts some personal freedoms and allows the government to bypass parliament with emergency decrees - for nearly two years following an abortive military coup in July 2016. Erdogan blamed the coup on his former ally, US-based Muslim cleric Fethullah Gulen, and has waged a sweeping crackdown on the preacher's followers in Turkey. The United Nations say some 160,000 people have been detained and nearly as many more, including teachers, judges and soldiers, sacked. The president's critics, including the European Union which Turkey still nominally aspires to join, say Erdogan has used the crackdown to stifle dissent. Few newspapers or other media now openly criticise the government and he has received far more election coverage than other presidential candidates. Erdogan, who defends his tough measures as essential for national security, told his supporters at rallies on Saturday that if re-elected he would press ahead with more of the big infrastructure projects that have helped turn Turkey into one of the world's fastest-growing economies during his time in office. "If he wins, I think the obstacles before us will disappear and we will have control," said Nesrin Cuha, 37, a call centre worker, who wore a headscarf. Religiously observant Muslims form the bedrock of Erdogan's support. "The opposition will not be a nuisance anymore with the new presidential system," said another Erdogan supporter, retired sailor Engin Ozmen, 60. Voting on Sunday starts at 8 am (0500 GMT) and ends at 5 pm (1400 GMT). Nearly 60 million Turks are eligible to vote, out of a total population of 81 million. Polls show Erdogan falling short of a first-round victory in the presidential race but he would be expected to win a run-off on July 8, while his AK Party could lose its parliamentary majority, possibly heralding increased tensions between president and parliament. Other presidential candidates include Selahattin Demirtas, leader of the pro-Kurdish Peoples Democratic Party (HDP), who is now in jail on terrorism-related charges that he denies. If the HDP exceeds the 10 percent threshold of votes needed to enter parliament, it will be harder for the AKP to get a majority. In a final appeal for votes in a video clip from his high security prison, Demirtas said: "If the HDP fails to get into parliament, all Turkey will lose. Backing the HDP means supporting democracy."