By Tim Cocks
LAGOS (Reuters) - Nigerians will vote on Saturday in what could be their most credible and close electoral contest since military rule ended nearly a quarter of a century ago - and the first in which a presidential candidate who is not from one of the two main parties stands a chance.
Former Lagos governor Bola Tinubu of the ruling All Progressives Congress (APC) faces Atiku Abubakar of the main opposition Peoples Democratic Party (PDP) and Peter Obi, a wild- card candidate who defected from the PDP to the smaller Labour Party and now leads in at least five opinion polls.
Obi, 61, has used a slick social media campaign to galvanise the vote of restless and increasingly disaffected youth, fed up with traditional politics and the old men who tend to dominate them - Tinubu and Abubakar are both in their 70s.
But analysts question whether the polls Obi leads are reliable and note he does not have the resources or extensive political base - built up over decades - that the other two have.
Whoever Nigerians choose to succeed President Muhammadu Buhari - only the second incumbent in Nigerian history to bow out willingly after serving two democratic terms - will have to resolve a litany of crises that have worsened under the retired army general's administration.
These include banditry and militant violence now affecting most parts of the country, systemic corruption that deters investment and enriches a well-connected elite, high inflation and widespread cash shortages after a botched introduction of new bills late last year.
All three candidates have made roughly similar promises to tackle these issues.
Amid fears that a close poll may be disputed and trigger even more violence and chaos, all candidates signed a peace pledge on Wednesday, promising to seek redress the courts for any grievances.
"This is the only country we have, and we must do everything to keep it safe, united and peaceful," Buhari said at the signing in the capital Abuja. "There should be no riots or acts of violence after the announcement of the election results."
Voters will also choose new parliament members.
"This is one of the closest elections that has ever been held in the history of this country," Abiodun Adeniyi, professor of mass communication at Abuja's Baze University, said.
POLLS QUESTIONED
All the polls showing Obi in the lead had a high number of respondents - on average around a third - who were undecided or unwilling to say who they would vote for. They also tended to target internet-savvy, educated types, and one required a smart phone to participate.
"We must take these polls with a generous amount of salt," said Nnamdi Obasi, senior Nigeria advisor for the International Crisis Group think tank.
"The samples are small (and) ... these are online polls with literate people, but there are large numbers of people who are not literate and not online, especially in the north."
Obi's known support base is in the south, whereas Abubakar and Tinubu are both popular in the north.
Though the contest looks close, Nigerian electoral law makes a run-off unlikely, as the winning candidate needs only a simple majority, provided they get 25% of the vote in at least two-thirds of the 36 states.
Spreading insecurity - especially Islamist violence in the northeast and banditry in the northwest and southeast - threatens to make voting impossible for many thousands of Nigeria's 93.4 million registered voters.
But an increasingly professional Independent National Electoral Commission (INEC) has made strides in tackling fraud that marred previous polls. A law enacted last year provides for electronic voting machines, card readers to confirm voters are registered in a central database, and the cancellation of results from polling centres where the ballots cast exceed registered voters.
Many Nigerians now trust the process.
"We thank God the election is going to be fair this time," said Ngozi Nwosi, 51, who sells clothes at a Lagos market stall, her voice barely audible above cheering and traditional drumming during a rally for her preferred candidate, Tinubu. "We trust INEC. Nigerians (will) go vote (and) get who they voted for."