Lagos: Nigeria, Africa`s most populous country and top economy, holds general elections on March 28, in what is expected to be the closest vote since independence from Britain in 1960.
Here are five key battleground areas where the outcome could tip the result in favour of President Goodluck Jonathan`s People`s Democratic Party (PDP) or the opposition All Progressives Congress (APC), led by ex-military ruler Muhammadu Buhari.Lagos, in the southwest, is the largest city in sub-Saharan Africa with an estimated population of 20 million and has 5.8 million registered voters.
The city`s government has been controlled by the opposition since military rule ended in 1999.
But the PDP has performed well in Lagos in past presidential elections and Jonathan will need some support in the city to secure re-election.
Lagos is the most religiously and ethnically mixed part of the country, where inter-marriage among faiths and tribes is widespread and where voters have a track record of transcending sectarian biases that shape voting in the rest of the country.
Both Jonathan and Buhari have campaigned aggressively in the key swing state and experts say the result is likely too close to call. Buhari won Nigeria`s second most populous state in 2011 by more than one million votes but will need to make gains in Kano to beat Jonathan nationally, after losing to the president by more than 10 million votes four years ago.
Buhari is from neighbouring Katsina state and his popularity has grown in the north over the last four years, with the region desperately wanting to retake the presidency from the mainly Christian south.
Three other factors are likely to help Buhari among Kano`s five million voters:
- Governor Rabiu Kwankwaso defected from the PDP to the APC last year, meaning the state government machinery will for the first time be aiding the opposition.
- Ex-Kano governor Ibrahim Shekarau -- who has since joined the PDP -- was one of several opposition presidential candidates in 2011 and received more than 526,000 votes.
Buhari now leads a united opposition and could grab the support of those who backed Shekarau but equally the ex-governor`s supporters could still remain loyal to the PDP.
- Since Nigeria last voted, Kano has been hit by dozens of Boko Haram attacks. Those frustrated with Jonathan`s handling of the conflict may turn to Buhari, who has emphasised his national security credentials. Next to Jonathan`s home state of Bayelsa in the oil-producing south, Rivers should have been comfortable terrain for the president and the PDP.
The ruling party has won easy majorities in all governorship and national elections in Rivers since 1999.
But Governor Rotimi Amaechi, who defected to the APC, has become a vocal Jonathan antagonist and is serving as director general of Buhari`s campaign.
Amaechi is seen as desperately wanting to hand Jonathan a defeat in this former PDP stronghold and analysts say some of the state`s 2.5 million voters will follow their governor in backing Buhari. At first glance, the dynamics of this religiously divided northern state with 3.4 million registered voters appear to favour Buhari.
The opposition leader has lived in the state capital Kaduna city for most of his life and is a native son in the eyes of many voters.
But Jonathan ran neck-and-neck with Buhari in Kaduna in 2011 -- losing by about 150,000 votes -- and may do well there again.
The current Vice President Namadi Sambo is from Kaduna and carries some support, while the state government is still PDP-controlled.
The most crucial period in Kaduna may be after the results are announced. The state was the epicentre of post-election violence in 2011, which killed more than 1,000 people.Borno, in the northeast, has been brutalised by Boko Haram for six years but is not a battleground in terms of the electorate: Buhari is expected to win massively among a population that has voiced outrage over Jonathan`s handling of the Islamist uprising.
The election battle in Borno may instead centre on logistics and legalities.
Hundreds of thousands of people forced from their homes by the fighting have been told they can vote in displaced persons camps.
But the details of this emergency arrangement could prove complicated -- and may be subject to legal challenge -- possibly fuelling tension in an already restive region.