Lagos: Retired Major General Muhammadu Buhari has tried three times to become president of Nigeria since the return to civilian rule in 1999 -- and failed on each occasion.
The 72-year-old was Nigeria`s military ruler from December 31, 1983 to August 27, 1985 after he ousted elected president Shehu Shagari, whose government was widely seen as corrupt and inept.
One former senior military officer told AFP that Buhari, a devout Muslim, was "exceptionally corruption-free" and, unusually for a Nigerian leader, did not accumulate much in the way of spoils.
But his harsh anti-corruption stance made him many political enemies, which could hinder his return to high office.
Buhari began his military career in 1962 and during his short time in power was notorious for draconian decrees, a crackdown on "indiscipline" and human rights abuses.
In particular, the execution of three young men, found guilty retrospectively of drug trafficking, triggered domestic and international outrage.
Critics of his regime were thrown in jail, among them the Afro-beat legend Fela Kuti for an alleged currency violation but which critics said was politically motivated.
Buhari was also at the centre of a major diplomatic row with former colonial power Britain after attempting to smuggle Shagari`s former adviser Umaru Dikko from London to Lagos.
Dikko, who had fled to the British capital after his boss` ouster, was found drugged in a crate at Stansted Airport.
The British satirical magazine Private Eye lampooned the incident with one of its most famous headlines: "Fly Nigeria -- It`s a crate way to travel."
After his ouster by Ibrahim Bagangida in 1985, Buhari, who had once served as oil minister in the 1970s, slipped out of public life.
But he made a return 20 years later as head of a government agency funding development projects with additional revenue from oil sales, where he demonstrated an autocratic but effective style."He is not very communicative, he is reticent but quite knowledgeable without flaunting it," said Ayo Banjoko, a Lagos-based political analyst.
"He is imbued with a messianic zeal. He has a rigid and intransigent disposition and he believes this country must and should be purged of its ills, especially corruption."
Buhari`s quest for a return to high office saw him seek the presidency under two different political parties, in 2003, 2007 and 2011.
He lost out to Olusegun Obasanjo, Umaru Musa Yar`Adua and Goodluck Jonathan respectively.
Buhari complained of gross irregularities in all three polls but won a landslide victory in APC primaries to take on Jonathan again and the ruling PDP.
But although billed by the APC as the man to rid Nigeria of endemic graft and end the Boko Haram insurgency, he has had to face multiple attacks from the administration in Abuja.
He has been portrayed as a religious zealot and it was claimed that he was ineligible to even stand as he could not initially prove that he had finished his secondary education.
But the APC has brushed off the claims as an attempt to divert attention away from the government`s record.
In July 2014, Buhari narrowly escaped death after a suicide attack on his car as it travelled through the northern city of Kaduna: 42 people were killed and Boko Haram militants blamed.
Two months earlier, Buhari had criticised Boko Haram as "mindless bigots masquerading as Muslims" for kidnapping more than 200 schoolgirls from northeastern Nigeria. Some analysts have however not ruled out that the bombing may have been politically motivated.