Nigeria's presidential election is a very tight race that many analysts say is too close to call. Here's a look at the two front-runners in the race.

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GOODLUCK JONATHAN

The 57-year-old incumbent and ruling party candidate has been called an "accidental president." The soft-spoken marine biologist became governor of Bayelsa state after the impeachment of its elected governor. Jonathan later became vice president and then president after elected Muslim leader Umaru Yar'Adua died in 2010.

In 2011 he was re-elected with an easy margin of millions of votes over his current rival Muhammadu Buhari.

But Jonathan's insistence on running again after he was presented as the sole candidate at engineered party primaries has torn apart his party which experienced dozens of high-level defections to a new opposition coalition. His detractors say he has broken an unwritten party rule to rotate power between the mainly Christian south, from which he hails, and the predominantly Muslim north, endangering a careful balance of power in the volatile nation beset by an Islamic uprising in the northeast.

Jonathan's economic achievements have been overshadowed by his administration's failure to curtail the insurgency. The military announced Friday, the eve of the vote, that it has cleared Boko Haram from all three northeastern states but this was dismissed by man is seen as a political ploy to win votes.

The president's government has succeeded in a mini agricultural revolution, galvanizing farmers to triple production of basics like rice, reducing dependency on imports. Jonathan also has pushed through the privatization of the troubled electricity sector, though the benefits are yet to be felt in the nation where more than 60 million are without any form of power and industry suffers from chronic blackouts.

Under Jonathan, Nigeria rebased its economy to become the largest in Africa at $510 billion. But that has brought little comfort to the 70 percent of the 170 million people who live in poverty because of rampant corruption that Jonathan has not tackled, according to analysts.

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MUHAMMADU BUHARI

The 72-year-old who ousted a democratically elected government first came to power in a 1983 coup.

His regime executed drug dealers, returned looted state assets and sent soldiers to the streets with whips to enforce traffic laws. Government workers arriving late to offices were forced to perform frog squats. His "war against indiscipline" won many followers, though his regime detained journalists critical of the government and laws were passed allowing indefinite detention without trial.

Despite his recent assurances that he is a convert to multiparty democracy, some worry the perennial candidate, running for president for the fourth time, could return to his autocratic ways.

But some Nigerians sickened by the growing corruption under Jonathan's administration say the austere Buhari's honesty and strictness is what the country needs. In addition, his background in the military is seen as invaluable in the fight against Boko Haram.

Many of Buhari's past stances have come to haunt him in this election, including statements in the 1980s that he would introduce Islamic Shariah law across Nigeria. A moderate form of Shariah was introduced in northern states in the 1990s but it operates alongside Western-style courts and only in majority-Muslim states.

Buhari also has been criticized for calling the military state of emergency imposed in the northeast to fight Boko Haram as a campaign against northerners, and for suggesting that the government should parlay with the Islamic extremists and offer them amnesty, as it has oil militants in the south. Lately, however, he has campaigned on a promise to wipe out the group that recently pledged allegiance to the brutal Islamic State operating in Syria and Iraq.

Buhari has made extravagant election pledges including to introduce universal health care.