Buhari is personally clean, but his anti-corruption measures almost exclusively targeted politicians of other parties. Nigerian average incomes fell by more than a third and unemployment doubled on his watch (mostly because of the collapse in oil prices). He didn't deliver on his promise to eliminate the Islamist extremists of Boko Haram, affiliated with ISIS, who have terrorised the northeast of the country.
He is also so lethargic, perhaps due to chronic illness, that he is popularly known as "Baba-Go-Slow". He took six months to name his cabinet, and he was abroad so long on sick leave (five months) that when he finally came home conspiracy theorists claimed that he had died and been replaced by a body double ("Jubril from Sudan") who had undergone plastic surgery.
Buhari should lose, and he probably will, because three ex-generals (all former presidents) who once backed him have switched to his challenger, businessman Atiku Abubakar. "Atiku" is a billionaire who started out as a humble customs officer. People speculate that this made him very useful to generals and other powerful people who wanted to parlay a small fortune into a big one.
Be that as it may, Atiku then went into the oilfield supply business and prospered mightily (maybe with a little help from his friends). He served two terms as vice-president, after the first of which he was accused of having diverted $125 million of public funds to his own business interests.
A US Senate report in 2010 accused him of having transferred $40m of "suspect funds" to the US, using his American wife's bank account, but he has never faced a court. But he vows to use his skills as an entrepreneur to sort out the country. If he succeeds, and some of the money sticks to him, who cares? At least it can be said on his behalf that he supports Arsenal.
This is the choice that faces Nigeria, and it's really no choice at all. Both candidates embody exactly the characteristics that define the country's problems.
First, they are very old – Muhammadu Buhari is 72, Atiku Abubakar is 72 – in a country where half the voters are under 35, and half the population is under 18. The country is run by a congeries of mostly rich old men, mainly for their own benefit, and it has been thus ever since the return of democracy 20 years ago. Before that it was run by a bunch of somewhat younger soldiers, also mostly for their own benefit.
Nigerian politicians switch parties as often as they change wives, and show only rhetorical concern for the 10 million young people who are unemployed. You would think that such a system could not survive, and perhaps one day it will be swept away, but there is no sign of it happening in this election.
The other thing the two chief presidential candidates have in common is a plethora of children. Buhari has 10 offspring from two marriages (one after the other). Abubakar has 28 children from four marriages (simultaneous). Humbler people can't afford quite that many, but most people are doing their bit to ensure that Nigeria's population outgrows its resources.
This is a sensitive topic, obviously, but not to talk about it is to ignore Nigeria's biggest problem. In 1960 Nigeria had a quarter of the population of the United States. Now it has more than half as many people, and by 2050 it will overtake the United States to become the world's third most populous country.
At that point it will have over 400 million people. Nigeria is only slightly larger than Texas (pop. 28 million).
It will probably be a "free and fair" election next Saturday, but it won't change any of that.
Gwynne Dyer's new book is 'Growing Pains: The Future of Democracy (and Work)'.