General elections in Nigeria between 12 April and 3 May are the first since a 1999 ballot that ended more than 15 years of military rule.
Responsibility for organising the elections lies with the Independent National Electoral Commission (INEC), headed by Abel Guobadia, a former university lecturer.
Up for grabs are the posts of president, governor of each of Nigeria's 36 states, federal parliamentarian and member of each state legislature. No date has been fixed for local government elections - due since last year but postponed because of delays in revising the voter's register, which is the responsibility of the electoral commissions of the different states.
Nigeria has a presidential system of government, modelled after that of the United States. There is an executive president, who is head of state and government and chooses his own ministers with the approval of the legislature. Lawmaking responsibility lies with the legislature, which comprises the Senate and House of Representatives. A similar relationship exists in each state between the governor and the state legislature, and between local government chairmen and their councillors.
The elections begin on 12 April when eligible voters among the country's 120 million people select the members of the federal legislature. They return to the polls on 19 April to elect a new president and the governors of their respective states. If no clear winners emerge, presidential and governorship run-offs will follow on 26 April. Finally, electors in each state will choose their legislators on 3 May.
To win the vote, a presidential candidate will have to obtain the highest number of votes and win at least 25 percent of the ballots cast in two-thirds of the country's 36 states.
Similarly a governor will have to obtain the highest number of votes in his state and at least a quarter of the ballots cast in two-thirds of the local government areas in the state.
Of the 30 political parties registered for this year's elections - as against three in 1999 - only 20 are fielding presidential candidates, according to INEC.
As a result of internal problems within the People's Democratic Party (PDP), the ruling party is weaker than it was four years ago. However, it appears to be in the best position to win the presidential election and a majority of the seats in the federal and state legislatures. Many of its former staunch members have left for other parties after complaining of alienation by the main party caucus formed around Obasanjo. It is telling that Jim Nwobodo, the presidential candidate of the United Nigeria People's Party, and Ike Nwachukwu, the candidate of the National Democratic Party, are senators elected on a PDP ticket. Don Etiebet, the current chairman of the ANPP, had sought to run for president for the PDP in 1999.
The PDP faces the strongest challenge from the All Nigeria People's Party (ANPP), whose candidate, Muhammadu Buhari, like Obasanjo, was a former military ruler. The PDP has pitched its campaign on the need for continuity, to give Obasanjo and Vice President Atiku Abubakar another four years to finish the "good work" they started. ANPP, on the other hand, has been emphasising the urgent need for change, pointing to what it considers the failings of the ruling party: widespread insecurity, poor roads despite expenditure of huge sums, continuing fuel scarcity and persisting power cuts.
Most of the other oppostion parties have also been highlighting similar "failings" of the government. Others, such as the All Progressive Grand Alliance (APGA), led by former secessionist Biafra leader, Emeka Odumegwu Ojukwu; the National Conscience Party (NCP) led by radical lawyer Gani Fawehinmi; and Green Party of Nigeria, led by human rights lawyer and pro-democracy activist, Olisa Agbakoba, have promised to call a "sovereign national conference" of the country's more than 250 ethnic groups, if they win. The purpose will be to "renegotiate the basis of Nigerian unity", devolve more powers to the regions and address the fundamental issues that cause friction between the country's communities.
For Ojukwu, whose secessionist and civil war credentials may not enamour him to many people outside the Igbo-dominated southeast, renegotiating Nigeria appears to be a key object of his candidacy. "We know we're not likely to win the presidency but the party is hoping to win enough states and seats in the southeast to improve its bargaining position," APGA member Uche Eze told IRIN.
NCP, Democratic Alternative and the Green Party all grew out of the pro-democracy movement that battled successive military rulers from the mid-1980s. They are all against World Bank- and International Monetary Fund-backed policies such as privatisation, removal of subsidies and devaluation implemented during the years of military rule. They have promised to revisit these policies if elected and reverse what they consider the damage done by them.
Another issue on which most parties have an opinion is the restiveness of the Niger Delta region, which produces most of the oil that makes Nigeria one of the world's top ten exporters. Much of the violence in the region in recent years has been spurred by demands by the inhabitants for a greater share of the oil wealth produced there.
Where Obasanjo has been reluctant to give up the federal share of oil revenue, most of the opposition parties are promising to pay more. Buhari has pledged to raise the oil states' share to 30 percent of all oil revenue against 7.5 percent currently paid by Obasanjo. The more radical parties who want to "renegotiate Nigeria" and devolve more powers away from the centre, want the regions to retain at least 50 percent or even all of the revenue, in some cases, and pay taxes to the central government.
But in a country where more than 70 percent of the populace are illiterate and live below the poverty line, issues have not always won elections. In the past there had been either outright rigging of votes by the powerful or the use of financial inducements to sway voters. Concern has also been expressed by many about increasing political violence, characterised by cases of political assassination and fighting between thugs hired by various political factions to intimidate their opponents. These have been major concerns of international and local election monitors.
In a recent pre-election assessment report, monitors from two US institutions, the National Democratic Institute and The Carter Centre drew attention to such issues which, they said, might undermine the credibility of the elections. Particular concern was expressed in the report over the apparent absence of a "well-publicised national security plan" to deal with a growing wave of political violence
Equally troubling, the report said, was the "absence of public scrutiny of campaign finance" and the lack of a "mechanism for investigating reports of abuses" despite the well-known "corrosive influence of money" in Nigerian politics. President Obasanjo has raised five billion naira (US $39.37 million), the highest amount collected by any candidate, for his campaign. Other candidates have also raised huge sums, but it is not clear if the money would only be used for campaign logistics, advertising and publicity or whether it might be misappropriated as widely suspected.
However, international and local monitors are already set to see things for themselves. Both the European Union and the Commonwealth have sent in hundreds of monitors and observers. Other independent international human rights and good governance groups are also sending observers. A coalition of local human rights and civil society groups, known as Transition Monitoring Group, is putting out 10,000 election monitors nationwide.
On each election day, according to the schedule released by INEC, ballots are to be cast between 8.00hrs and 15.00hrs local time. Final results from all over the country of 120 million are expected within two days.