The people of Nigeria, Africa's most populous country with the continent's largest economy, were meant have begun voting yesterday in the second stage of a general election against the background of an existential national crisis.

Instead the poll has been postponed five weeks amid the turmoil of an intensifying Islamist insurgency that has taken thousands of lives and displaced millions; financial chaos resulting from the falling price of oil, on which the state depends for 70 percent of its revenues; burgeoning corruption at every level; and now fears of a rising constitutional crisis.

It all adds up to a perfect political storm which many fear could plunge the country of 175 million people and more than 250 ethnic groups into a devastating civil war or lead to a military coup. Not since the advent of black majority rule in South Africa in 1994 does so much hang on the success, or otherwise, of an African election.

Elections to the governorships of the vast country's thirty-seven states and the state assemblies have been postponed for six weeks until 11 April. The key presidential and National Assembly elections, pitting incumbent Goodluck Jonathan against former military ruler Muhammadu Buhari, had been scheduled for 15 February but were delayed until 28 March.

The chairman of the national Electoral Commission, Attahiru Jega, postponed the polls under heavy pressure from armed forces and intelligence chiefs who said they were unable to guarantee safety at voting stations while at the same time launching a new military campaign against well-organised insurgents who have established an Islamic State about half the size of Scotland in the impoverished northeast bordering Cameroon and Chad.

But many Nigerians see the concern about the insurgency, however understandable, as a pretext conjured up by President Jonathan and his ruling People's Democratic Party (PDP) to forestall almost certain loss of power in the various polls. There are growing fears within Buhari's opposition All Progressives Congress (APC) and among civil society groups that Jonathan's government might try to extend its mandate - beyond a four-year term that ends on 29 May - or even risk surrendering the country back into the hands of the military rather than allow a Buhari/APC victory.

"The security pretext is obviously disingenuous," said Africa expert Stephen Chan, Professor of World Politics at the University of London's School of Oriental and African Studies. "Boko Haram [the Islamic insurgents' name, meaning "Western education is forbidden"] cannot be defeated in that time [by the dates of the rescheduled polls], despite a major government offensive ... In fact, of a 130,000-strong Nigerian army, only about 30,000-40,000 are fighting in the northeast.

"The tragedy in Nigeria is not what is already a botched election, but that within the election there is almost no mention of the victims of Boko Haram. The Chibok schoolgirls are not a campaign issue. What to do long-term about Islamic insurgency is not an issue. Good luck Johnson has no policies about how to make the (largely Muslim) north as prosperous as the (mainly Christian or animist) south."

Ten months ago 276 girl students were kidnapped by Islamic Jihadists of Boko Haram from the Government Secondary School in the mainly Christian small town of Chibok in Borno State, in the far northeast corner of Nigeria along the southwestern shore of Lake Chad. The children were aged 16 to 18 and were in their final year of school. Amnesty International said the Nigerian military had four hours advanced warning of the mass kidnapping, but failed to send reinforcements to protect the school. The students were forced to convert to Islam and into marriage with Boko Haram fighters with a reputed "bride price" the equivalent of £7.50 each. Most were taken to Borno's dense Sambisa Forest, where the insurgents have secure bases, or across the border into Chad and Cameroon. Yesterday, thousands of people marched in Cameroon's capital, Yaounde, to protest against Boko Haram's insurgency.

In the months since the Chibok girls disappeared the whole of the northeast, many parts of the rest of the north and parts of the centre and south have become a bloodbath with Boko Haram massacring villages more or less every day, slaughtering people, beheading "enemies of Islam" and loading sophisticated videos of the grisly executions on to social media.

Last week, in the most recent wave of Boko Haram attacks, more than eighty people were killed in northern Nigeria. A suicide bomber killed at least 17 people at a bus station in Biu, in southern Borno, witnesses say, while a second bomber was caught by a crowd and beaten to death. In Jos, the capital of Plateau State, three bombs thrown from a car killed 15 people at a bus station and the university. Other attacks in the northern city of Kano and the town of Potiskum claimed more than fifty lives.

Lamido Sanusi, until last year Governor of the Central Bank of Nigeria but now Emir of Kano, one of the most influential Moslem fiefdoms in northern Nigeria following the death of his 83-year-old uncle, Ajhaji Ado Abdullahi Bayero, said the rise of Boko Haram has exposed the incompetence and corruption of the central government. Sanusi was sacked by Goodluck Jonathan when he told the President that £13 billion had mysteriously gone "missing" from Nigeria's national oil accounts. "Jonathan took it personally," said Sanusi. "Basically, I have no friends left in Abuja (the national capital in central Nigeria)."

Sanusi is the Emir or King of a desert city that is home to 10 million people. Kano is built around a 1,000-year-old caravanserai or resting place where for fifty generations Arabia has met Africa on the southern edge of the Sahara. Sanusi, who attended a Catholic school and worked for Citibank on Wall Street, said: "I fought the National Assembly over their pay. Nigerian MPs receive salaries of £130,000 plus yearly expense allowances of £650,000. I said half the civil service should be fired. I said the petroleum minister was leasing her own private planes to the government, paying herself every time she took a flight."

Emir Sanusi, one of the many Muslim opponents of both Boko Haram and the central government, went on: "A state fails when its leadership fails. I am not very optimistic. Our citizens are left on their own to perform the functions of a state. I think we have all the symptoms of a failing state ... The people are seeing how Boko Haram is killing people and just walking away, while the army is doing nothing about it."

He said it is important to understand how Boko Haram learned its Syrian Islamic State (IS)-style behaviour. "You have to make the connection between the million US dollar shopping sprees of the rich and the maternal death rate, the child death rate, the low life expectancy, the malnutrition," he said. "That money could save people. This is murder. Worse, the people taking all the money are the people entrusted with protecting those lives. They were voted in by the same people they are killing."

Various opinion polls have placed Jonathan and Buhari roughly neck and neck in the Presidential race. But members of General Buhari's APC are convinced that the man who ruled as a military dictator from 31 December 1983 before being overthrown himself in a coup on 27 August 1985. His allies believe he is among the few politicians with the stature capable of stopping the country's current rot and restoring fighting spirit to the demoralised army in the war against Boko Haram. The ascetic Buhari dismisses Boko Haram as an "unIslamic band of criminals." The Buhari years in power are remembered for his attempts to impose discipline on Nigerians, including sending rifle-toting and whip-wielding soldiers into airports and to bus stops to force passengers to queue in rigidly straight military lines.

APC members are convinced their candidate can win outright in the first Presidential round on 28 March. This would require the 73-year-old former military ruler, born the youngest of his father's twenty-four sons in the far northern state of Katsina, to gain more than 50 percent of the overall vote. To avoid a run-off in the complex Nigerian constitutional system, designed to ensure that Presidential candidates gain support from most communities, he would also have to win 25 percent or more of the votes in at least 24 of the 37 states in the federation, including from some of President Jonathan' s Christian strongholds in the deep south.

Goodluck Johnson was Nigeria's Vice-President when the incumbent head of state, Umaru Yar'Adua, a northern Muslim, died from heart and kidney problems in 2010. Johnson, born into a family of canoe makers in the Niger Delta where most of Nigeria's oil wealth is produced, succeeded Yar'Adua and won a general election in 2011.

He was initially widely perceived as a breath of fresh air. His government privatised the chronically inefficient electricity sector and tackled fraud in the distribution of fertiliser. Under Johnson, the political elite continue to operate with breathtaking shamelessness. Farouk Lawan is a government MP who exposed the details of a fuel subsidy scam which had cost the country £4.4 billion. Yet he was secretly filmed later by a newspaper accepting £325,000 in cash from a businessman whose company was under investigation.

Transparency International, the Berlin-based corruption-monitory group, rates only Haiti and Bangladesh as more corrupt than Nigeria, where navigating the most basic government services, such as getting freight through customs, requires a bribe. In Abuja, motorists have little choice but to pay police officers - many armed with automatic rifles - who set up impromptu roadblocks to demand a "kola nut," local jargon for a wad of money. Politicians in the capital both take bribes and give them, including payments to reporters who can make more money from politicians' sweeteners than from their newspaper pay.

President Johnson has lost much of his initial goodwill. He has been clumsy in handling the Boko Haram insurgency and appears unfazed by the alarming levels of graft within government circles. Facing a growing protest vote, he has been booed and heckled at rallies and in some northern states his official convoy has been stoned. His election team hope that a belated, successful military offensive against the Boko Haram insurgents, together with the advantages of incumbency, will swing things back in their man's favour.

The weeks ahead of the postponed elections will be nerve-racking. Many Buhari supporters in the north believe they have already won. There will be huge unrest if they feel they have been cheated of victory either by manipulation of the votes or by a military coup.

Meanwhile in the Niger Delta many of President Jonathan's supporters feel passionately that he is entitled to a second term. Former warlords from the days when the oil-producing region was in conflict have threatened openly to take up arms again should he lose.

No outcome will be entirely smooth. But the potential for instability in the north, where the majority of people feel they have not enjoyed the benefits of civilian rule, is obviously most dangerous, given the new opportunities an uncertain or rigged outcome would provide for Boko Haram. Nasir el-Rufai, a former government minister contesting the Kaduna state governorship, warned: "These next weeks will be among the most dangerous in Nigeria's history."