Turks will vote on Sunday in one of the most consequential elections in modern Türkiye's 100-year history, with pre-election polls indicating President Recep Tayyip Erdogan faces an enormous challenge from his main opponent, Kemal Kilicdaroglu, after 20 years in power.

The vote will decide not only who leads Türkiye, a NATO-member country of 85 million, but also how it is governed, where its economy is headed amid a deep cost of living crisis, and the shape of its foreign policy, which has taken unpredictable turns.

Opinion polls give Kilicdaroglu, who heads an alliance of six opposition parties, a slight lead, but if either of them fails to get more than 50 percent of the vote there will be a runoff election on May 28.

The election takes place three months after earthquakes in southeast Türkiye killed more than 50,000 people. But little evidence suggests it has changed how people will vote.

Voters will also elect a new parliament, likely a tight race between the People's Alliance comprising Erdogan's conservative Islamist-rooted AK Party (AKP) and the nationalist MHP and others, and Kilicdaroglu's Nation Alliance formed of six opposition parties, including his secularist Republican People's Party (CHP), established by Türkiye's founder Mustafa Kemal Ataturk.

Polls will open at 8 a.m. (0500 GMT) and close at 5 p.m. (1400 GMT). Under Turkish election law, the reporting of any results is banned until 9 p.m. By late on Sunday there could be a good indication of whether there will be a runoff vote for the presidency.

Kurdish voters, who account for 15-20 percent of the electorate, will play a pivotal role, with the Nation Alliance unlikely to attain a parliamentary majority by itself.

The pro-Kurdish Peoples' Democratic Party (HDP) is not part of the main opposition alliance but fiercely opposes Erdogan after many of its members were removed from local government positions in recent years.

The HDP has declared its support for Kilicdaroglu in the presidential race. It is entering the parliamentary elections under the emblem of the small Green Left Party due to a court case filed by a top prosecutor seeking to ban the HDP over links to Kurdish militants, which the party denies.

(With input from Reuters)