Lagos: Africa`s most populous country and top economy, Nigeria, holds general elections on Saturday.
The contest between President Goodluck Jonathan of the Peoples Democratic Party (PDP) and Muhammadu Buhari of the opposition All Progressives Congress (APC) is expected to be the closest since independence from Britain in 1960.
Here are some key numbers: It may be a mouthful but it is the only way for a presidential candidate to secure a first-round win.
To avoid a run-off, candidates need to have won the most votes and at least 25 percent support in two thirds of Nigeria`s 36 states and the Federal Capital Territory of Abuja.
The latter measure was implemented to ensure that all presidents have at least some nationwide support in a country divided by religion and ethnicity.
The number of registered voters, according to the Independent National Electoral Commission (INEC).
With a population of roughly 173 million, Nigeria is the world`s sixth-largest democratic country. INEC says it will take 10 seconds for new card readers to authenticate a voter.
Nigeria is using electronic card readers for the first time, which the electoral commission maintains will all but eliminate voter fraud -- a chronic problem in past elections.
If effective, the devices could make the 2015 polls the cleanest ever in the country`s history.
Some in the PDP have criticised the new authentication system, calling it untested and casting doubt on polling officials` ability to use the technology.
If a significant number of card readers fail at polling stations, frustration and delays could lead to unrest in the closely fought vote. The minimum number of people in the northeast believed to have been forced from their homes by Boko Haram`s Islamist uprising.
Nigeria`s electoral act says people can only vote at the polling stations where they are registered, typically near their home.
An emergency measure has been agreed to allow people to vote in displaced persons camps.
But given the uncertainty and last-minute nature surrounding procedures, confusion and disputes are possible.
The northeast is an opposition stronghold. Mass disenfranchisement in the region will likely hurt Buhari`s chances. The number of elections, including Saturday`s vote, since military rule ended in 1999.
The PDP did not face a serious challenge in any of the previous polls (1999, 2003, 2007, 2011).
Frustration over corruption, six years of Boko Haram violence and a stronger opposition are seen as the main reasons why the ruling party is vulnerable this year. The average price in US dollars of a barrel of crude on March 25, according to OPEC, after selling above $100 at various points in 2014.
Nigeria derives more than 70 percent of government revenue from crude sales and the dramatic slide in the price of oil has hit the economy hard.
The naira currency, which was selling on the street at 180 to the dollar earlier this year, is now selling at 220 per $1.
The role of money in Nigerian politics has been well documented, including widespread allegations of vote-buying on past election days.
The cash crisis could therefore have a significant impact on Saturday`s result and its aftermath, providing an urgent headache for the new administration.