After 16 years in power, Turkish President Recep Tayyip Erdogan is used to winning elections.
But this time, other candidates are offering real alternatives to his increasingly authoritarian rule.
And while he's clamped down on press freedom and on many of his critics, his opponents have harnessed social media to get their voices heard.
The nationalists: MHP
Erdogan's AK Party has formed an alliance with the hardline nationalists, the MHP.
As a result, MHP leader Devlet Bahceli has stepped aside and Erdogan is running as the MHP's presidential candidate as well.
The secularists: CHP
Founded by Mustafa Kemal Ataturk, the founder of the modern Turkish republic, the centre-left CHP, or Republican People's Party, is secular and social democratic.
A fiery and charismatic speaker, party leader Muharrem Ince is the most likely candidate to face Erdogan in a second-round run-off if no one wins a majority on Sunday.
The wild card: Iyi Parti
Wild card Meral Aksener heads the Iyi Parti - or Good Party. She's a liberal nationalist and secular conservative and many believe she would stand the best chance of carving off Erdogan supporters in a second-round head-to-head.
The Islamists: Saadet Parti
The Islamist Saadet Party has never had much luck at the ballot box but its current alliance with secularist and nationalist groups has boosted its chances of winning seats.
The party is targeting religious voters disillusioned with Erdogan and the AKP.
The pro-Kurdish party: HDP
Erdogan is still favourite in Sunday's (June 24) vote but his opponents are hoping his fracturing base will turn toward the other parties.
His hardline positions on Kurdish issues may have lost him the backing of even the most conservative Kurds, whose votes for the AKP helped bring him to power.
Meanwhile Selahattin Demirtas - the charismatic imprisioned leader of the pro-Kurdish HDP - managed to expand his constituency beyond the Kurdish community in 2015.
Demirtas has vowed to back anyone over Erdogan if the presidential vote goes to a second round.