Nigerians set to go to polls in referendum on Buhari's first term

Voters in Nigeria, Africa’s biggest country by population, go to the polls on Saturday to choose between the incumbent Muhammadu Buhari, his main rival, Atiku Abubakar and more than 70 other candidates.

Saturday’s election is seen as a referendum on Buhari’s first term, which has been marred by his prolonged absence due to illness, a weak economy, and the government’s failure to effectively tackle corruption and insecurity.

A faction of Boko Haram attacked a state governor’s convoy on Tuesday, killing four people and stealing vehicles. Elsewhere, 15 people were crushed to death at a ruling party rally in eastern Port Harcourt. On Thursday, 14 sacks of ballot papers were intercepted in Kano state – though police said they were merely “specimen” papers to educate voters.

As Nigerians prepared to cast their votes, data analysts raised concerns about the number of new voters registered since January 2018, which they said increased by almost exactly the same percentage in each of the country’s states, and suggested that the results of Saturday’s presidential election could be open to mass rigging.

Plotted on a scatter line graph, there was a 0.99 correlation across all the states, without a single outlier. According to three separate data analysts, the parity cannot be a coincidence, and two of them called it a “statistical impossibility”. “Only God works that closely,” one said.

But other observers said there were other possible explanations for the correlation, including demographics.

“In itself, it’s not an indicator of any kind of electoral malpractice or manipulation,” said economist Nonso Obikili. He said the correlation in the registration figures across states was “what you would expect, because demographic changes don’t happen very quickly”.

If some of the new voters registered are fake, it could imply meddling at the Independent National Electoral Commission (INEC) , though it is unclear whether it would be the ruling party or the opposition that would stand to benefit.

Additional data seen by the Guardian shows irregularities in registration for the 2015 election in which Buhari came to power, until now considered to have been free and fair.

On Sunday 16 February, 84m voters will choose who leads Africa’s largest democracy. Despite over 60 candidates, it is likely to be a choice between President Muhammadu Buhari, and former vice president Atiku Abubakar.

President Muhammadu Buhari (APC candidate)

Buhari's 2015 victory with his All Progressives Congress (APC) party was built on three promises: to rid Nigeria of endemic corruption, fix the economy and tackle security threats.

The government says it is making progress in the fight against Boko Haram, but it is now in its tenth year, and the economy entered and climbed out of recession under Buhari. Opponents say his government is failing to tackle corruption, while Amnesty International say the army has been responsible for human rights abuses.

After spending five months in Britain in 2017 receiving treatment for an undisclosed ailment, opposition groups said he was unfit for office, but Buhari, 76, says he is strong enough to serve.

Atiku Abubakar (PDP candidate)

Main opposition People's Democratic Party (PDP) candidate Atiku, 72, has been caught up in corruption allegations since serving as vice president from 1999-2007. He has repeatedly denied any wrongdoing.

He has promised business-friendly policies to double the economy to $900bn by 2025. He wants to privatise parts of the state oil company, and create a $25bn fund to support private sector investment.

Atiku's opponents have claimed he would exploit those pro-business policies to enrich himself and those around him.

A divided country

Nigeria is deeply divided between the mainly Muslim north and largely Christian south. There are more than 200 distinct ethnic groups. This has led to an unofficial power-sharing agreement, with the presidency alternating between north and south every eight years.

It isn't just religion or ethnicity causing fractures. Half of Nigeria’s registered voters are aged 18-35. Many say their ageing leaders are out of touch, and supported a "Not Too Young to Run" campaign to encourage younger people seeking office.

Election concerns

2015 was the only time Nigeria had a peaceful power handover since civilian government took over in 1999. Even then there was evidence of vote buying, voter intimidation, and other forms of corruption. International observers fear election interference and rigging this time around.

Last month, Buhari triggered a constitutional row when he suspended the chief judge, who has a crucial say in resolving election result disputes.

Path to victory

The candidate with the most votes is declared winner, as long as they have at least one-quarter of the vote in two-thirds of Nigeria's 36 states and the capital. Otherwise there is a run-off.

Martin Belam and agencies

An analysis of separate figures shows that manipulation may have happened in favour of Buhari’s party, which was running in opposition to Goodluck Jonathan’s People’s Democratic party. A clue may have been dropped last July when the INEC, perhaps inadvertently, publicly referenced a different set of results from the one on which Buhari’s victory was based.

Both documents showed 29.4 million votes were cast. But according to the original results, 31.7 million accredited voters participated in the election, whereas in the second set of results, that figure dropped to 23.6 million.

The discrepancy suggests an additional 6 million accredited voters, far more than the APC’s winning margin – as per the original result set – of 2.6 million votes.

Smartcard readers were used for the first time in 2015 and the second set of results was released in response to widespread criticism after the new technology malfunctioned, forcing millions of voters, including Jonathan, to use the manual process. The second set of results appears to have disappeared from the INEC’s website two months ago, along with all others relating to the 2015 poll.

Nigerian elections have a long history of rigging, and it is not usually limited to whichever side happens to be in power at the time. Powerful politicians move fluidly between the two main parties, taking support and manipulation mechanisms with them.

If free and fair, the election is expected to be very close, with many Nigerians either proclaiming themselves to be “Atikulated” and fed up with the state of the economy or chanting “Sai Buhari”, a term of respect used by those vigorously defending the president’s record.

In the ancient northern city of Kano, a Buhari stronghold, men in embroidered kaftan robes and colourful caps said they were voting for Buhari, while opposition billboards had been torn down in the streets. Innocent Okpanachi, an architect in Abuja, said: “The entire system is bad. You vote for who will unite the country.”

• This article was amended on 15 February to reflect doubts over the way in which analysts who spoke to the Guardian had interpreted new voter registration data for the 2019 election