Nearly 90 million people are eligible to vote in the election, which is taking place as Africa’s most populous democracy grapples with a multi-front security crisis, a sluggish economy and widening poverty.
For the first time since the end of military rule in 1999, a third serious candidate has emerged to challenge the dominance of the ruling All Progressives Congress (APC) and main opposition Peoples Democratic Party (PDP).
Polling stations were meant to open at 0730 GMT.
With Buhari stepping down after two terms in office, the APC’s Bola Tinubu, 70, a former Lagos governor and political kingmaker, says “It’s my turn” for the presidency.
He faces a familiar rival — PDP candidate and former vice president Atiku Abubakar, 76, who is on his sixth bid for the top job.
But the emergence of a surprise third candidate appealing to young voters, Labour Party’s Peter Obi, 61, has thrown the race open with his appeal for change from his old-guard rivals.
Nearly 10 million new voters registered this year, most of them under 34, representing an essential bloc if they come out to vote.
Cash and fuel shortages in the days before the election have left many Nigerians angry and struggling more than usual in a country already hit by more than 20 percent inflation.
Voters will also cast their ballot for Nigeria’s two houses of parliament, the National Assembly and Senate. Polls close at 1330 GMT.
The Independent National Electoral Commission (INEC) has given no timeline for results, but votes are expected to be tallied within a few days. Under a 2022 law, the official results have to be confirmed within 14 days.
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