Turks vote on Sunday in a presidential runoff that could see Tayyip Erdogan extend his rule into a third decade and intensify Turkey's increasingly authoritarian path, muscular foreign policy and unorthodox economic governance.

Erdogan, 69, defied opinion polls and came out comfortably ahead with an almost five-point lead over his rival Kemal Kilicdaroglu in the first round on May 14. But he fell just short of the 50% needed to avoid a runoff, in a race with profound consequences for Turkey itself and global geopolitics.

His unexpectedly strong showing amid a deep cost of living crisis, and a win in parliamentary elections for a coalition of his conservative Islamist-rooted AK Party (AKP), the nationalist MHP and others, buoyed the veteran campaigner who says a vote for him is a vote for stability.

Kilicdaroglu, 74, is the candidate of a six-party opposition alliance, and leads the Republican People's Party (CHP) created by Turkey's founder Mustafa Kemal Ataturk. His camp has struggled to regain momentum after the shock of trailing Erdogan in the first round.

The election will decide not only who leads Turkey, a NATO-member country of 85 million, but also how it is governed, where its economy is headed after its currency plunged to one tenth of its value against the dollar in a decade, and the shape of its foreign policy, which has seen Turkey irk the West by cultivating ties with Russia and Gulf states.

The initial election showed larger-than-expected support for nationalism - a powerful force in Turkish politics which has been hardened by years of hostilities with Kurdish militants, an attempted coup in 2016 and the influx of millions of refugees from Syria since war began there in 2011.

Turkey is the world's largest host of refugees, with some 5 million migrants, of whom 3.3 million are Syrians, according to Interior Ministry data.

Third-place presidential candidate and hardline nationalist Sinan Ogan said he endorsed Erdogan based on a principle of "non-stop struggle (against) terrorism", referring to pro-Kurdish groups. He achieved 5.17% of the vote.

Another nationalist, Umit Ozdag, leader of the anti-immigrant Victory Party (ZP), announced a deal declaring ZP's support for Kilicdaroglu, after he said he would repatriate immigrants. The ZP won 2.2% of votes in this month's parliamentary election.

A closely-watched survey by pollster Konda for the runoff put support for Erdogan on 52.7% and Kilicdaroglu on 47.3% after distributing undecided voters. The survey was carried out on May 20-21, before Ogan and Ozdag revealed their endorsements.

Another key is how Turkey's Kurds, at about a fifth of the population, will vote.

The pro-Kurdish Peoples' Democratic Party (HDP) party endorsed Kilicdaroglu in the first round but, after his lurch to the right to win nationalist votes, it did not explicitly name him and urged voters rather to reject Erdogan's "one-man regime" in the runoff.

'MORE ERDOGAN'

Polls will open at 8 a.m. (0500 GMT) and close at 5 p.m. (1400 GMT). By late on Sunday there should be a clear indication of the winner.

"Turkey has a longstanding democratic tradition and a longstanding nationalist tradition, and right now it's clearly the nationalist one that's winning out. Erdogan has fused religious and national pride, offering voters an aggressive anti-elitism," said Nicholas Danforth, Turkey historian and non-resident fellow at think tank ELIAMEP.

"More Erdogan means more Erdogan. People know who he is and what his vision for the country is, and it seems a lot of them approve."

Turkey's president has pulled out all the stops on the campaign trail as he battles to survive his toughest political test. He commands fierce loyalty from pious Turks who once felt disenfranchised in secular Turkey and his political career has survived the failed coup and corruption scandals.

Erdogan has taken tight control of most of Turkey's institutions and sidelined liberals and critics. Human Rights Watch, in its World Report 2022, said Erdogan's government has set back Turkey's human rights record by decades.

However, if Turks do oust Erdogan, it will be largely because they saw their prosperity, equality and ability to meet basic needs decline, with inflation that topped 85% in October 2022.

Kilicdaroglu, a former civil servant, has pledged to roll back much of Erdogan's sweeping changes to Turkish domestic, foreign and economic policies.

He would also revert to the parliamentary system of governance, from Erdogan's executive presidential system, narrowly passed in a referendum in 2017.