The man aiming to wrest the Nigerian presidency from Muhammadu Buhari has built a career circling the summits of public life.
Atiku Abubakar has been a top civil servant, a vice-president, and a prominent businessman and philanthropist, making his fortune in the oil sector and giving some of it away to charity.
The highest office in the land has, however, eluded him. On three occasions, he has tried for the presidency and fallen short. On 16 February, the 72-year-old tries again, offering his credentials as a seasoned political operator and serial entrepreneur as the remedy for Nigeria's ills.
However, his critics point to accusations of financial impropriety against him which they say make him unsuitable for top office in a country where corruption is a huge challenge.
He denies any wrongdoing and says the charges are politically motivated.
If elected, Mr Abubakar will be confronted by soaring unemployment, chronic poverty, a legislature gridlocked by regional rivalries, and a sluggish economy heavily dependent on fluctuating oil revenues.
His campaign is exploiting the contrast between his image and that of an incumbent who has become a target for much of the frustration over the economy.
Mr Buhari's critics say his personality - austere, aloof and inflexible - has proven ill-suited to the demands of governing Nigeria, even if it helped him win the last election, lending credibility to his pledge to fight corruption.
Mr Abubakar, by contrast, is an affable, enterprising figure, moving adroitly between the worlds of commerce and politics - qualities that, his supporters say, will help him unite the country and revive the economy.
Both candidates are from the mainly Muslim north of the country, and have tried to reach beyond their power base by choosing running mates from the mostly Christian south.
According to Cheta Nwanze, head of research at Lagos-based risk advisory SBM Intelligence, Mr Abubakar's campaign will hope to attract some of the people who voted for Mr Buhari in the last election - particularly "the educated youth that live in cities and have seen their incomes fall in the last few years".
Mr Abubakar is the candidate for the People's Democratic Party (PDP), the dominant force in Nigerian politics for the last two decades. He was with the PDP when it was formed at the end of a military dictatorship, and has served as vice-president in two of its administrations. However, he has had a tempestuous relationship with the party he helped create, twice having left it for opposition groups.
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His first exit, in 2006, coincided with an investigation into his record as vice-president, when he was accused of having diverted $125m (£95m) worth of public funds towards his business interests. Similar charges appeared in a 2010 US Senate report, which accused Mr Abubakar of having transferred $40m (£30.55m) of "suspect funds" to the US, using his American wife's bank account.
The charges have never been tried in court, and Mr Abubakar has rejected the allegations of corruption as politically motivated. In January 2019, he visited Washington DC, ending speculation that he was avoiding travel to the US because he might face arrest there.
According to Olly Owen, a lecturer in African studies at Oxford University, Mr Abubakar is the ultimate political insider.
"Back in the 1990s, when they were getting rid of military rule, he was in at the ground floor," he says. "He is a long-term power-broker, switching allegiances and dictating the nature of elite alliances."
Both candidates in the election are over 70, but Mr Abubakar's relative youth - contrasted with Mr Buhari's rumoured ill-health - is viewed as an asset in a country where most of the electorate is under 40.
Dr Owen says the two men appeal to two distinct tendencies among Nigerian voters - a yearning for clean government and a desire for economic opportunity.
"People are sick of corruption," he says, but on the other hand they are also "very entrepreneurial".
Tycoon and veteran power-broker
- Born in 1946 in northern state of Adamawa
- Co-owner of multinational oil services company that started life in a Lagos shipping container
- Oversaw privatisations during two terms as vice-president
- Fought against corruption charges, describing them as politically motivated
- Founded American University which gave scholarships to some of the "Chibok girls" who survived Boko Haram kidnapping
- His father, a devout Muslim, was briefly jailed for trying to stop him from attending a Western-style school
- An Arsenal football supporter, he has four wives and 28 children
Mr Abubakar's reputation in business is linked to the spectacular rise of Intels, the oilfield logistics firm that he co-founded in 1982. From its original office in a shipping container, the company has grown into a multi-national, multi-billion naira operation, employing more than 10,000 people.
He has diverted part of his wealth to charitable causes, most notably establishing the prestigious American University in Adamawa state, northern Nigeria. The university recently offered scholarships to some of the "Chibok girls" - survivors of a high-profile kidnapping by Islamist Boko Haram militants.
Mr Abubakar regards himself as a lucky beneficiary of the Western-style education offered at the university and fiercely opposed by Boko Haram. He was born in Adamawa to a devout Muslim family, and his father, a Fulani tradesman and herder, was briefly jailed for preventing him from attending school.
"Father was responding typically with fear and anxiety to the onslaught of change in Nigeria," Mr Abubakar writes sympathetically in his autobiography.
After finishing his studies, he joined the customs service, serving at Lagos port and airport. "Corruption was rife in Customs but I was not part of it," he writes. "I saw Customs… as a way of making money for the government."
While still a civil servant, Mr Abubakar began buying property and farmland for commercial purposes, eventually moving into the emerging market for oil and gas services. "I recognised very early in life that I have a good nose for business," he writes in a chapter of his autobiography entitled, Making Money.
His career in customs brought him into contact with the military and political elite, two categories that have been interchangeable for much of Nigeria's recent history. Mr Abubakar grew close to the former army major, Shehu Musa Yar'Adua, regarding him as a political mentor.
Against a backdrop of coups and crackdowns, the two men began networking with other regional leaders, hoping to form a credible government-in-waiting.
In 1989, Mr Abubakar quit the civil service to dedicate himself to politics. He made his first presidential run in 1991, as a candidate for the faction that had gathered around Shehu Yar'Adua. He would step down after coming third in the first round, and the election itself was later cancelled by the military government.
The repression intensified in the 1990s under the dictatorship of Gen Sani Abacha. Mr Abubakar was briefly exiled in London, while his mentor, Shehu Yar'Adua, was sent to prison and would eventually die there.
Mr Abubakar returned to Nigeria in 1997 as Gen Abacha relaxed his grip on power. He became vice-president after the elections in 1999 installed the PDP candidate, Olusegun Obasanjo, in the presidency.
During two terms in office, he oversaw a series of privatisations, earning praise as a liberaliser in some quarters, and criticism elsewhere as a crony capitalist.
In his autobiography, he takes credit for reforms of the banking sector, the auction of mobile phone licenses, as well as for an economic boom that enabled Nigeria to pay off much of its debt.
Mr Abubakar says he will bring back the good times if elected president in 2019. However, his ability to keep that promise will be subject to powerful forces outside his control.
"It's hard to predict what he could achieve," says the BBC's Nigeria editor, Aliyu Tanko, "with an economy that depends so heavily on the price of oil."
Mr Abubakar has four wives and 28 children.