ABUJA, Jan 13 (Reuters) - Thousands of Nigerian ruling party delegates flocked to a main square in the capital Abuja on Thursday to decide whether to back President Goodluck Jonathan as their candidate in April elections.
Such is the dominance of the People's Democratic Party (PDP) in Nigerian politics that whoever wins its primaries has in the past gone on to be the country's next ruler.
Historical precedent is on Jonathan's side. Should he be defeated in Thursday's vote, he would be the first sitting president to lose an election bid in Africa's most populous nation since independence from Britain in 1960.
"He's very confident. He was up all night visiting all the delegates ... He only finished about 9 a.m. this morning," Jonathan's campaign spokesman Sully Abu told Reuters.
But Jonathan's accidental route to power -- assuming the country's highest office when his predecessor, Umaru Yar'Adua, died last year -- means Nigeria is in uncharted waters.
His candidacy interrupts an agreement in the PDP that power should rotate between the mostly Muslim north and largely Christian south every two terms.
As a southerner, he faces stiff opposition standing for what would have been the second term of Yar'Adua -- a northerner.
Former Vice President Atiku Abubakar, a wealthy businessman from the northern Hausa ethnic group, is hoping to garner support from northern factions in the ruling party who fear their influence will wane should Jonathan win a four-year term.
"This election is one of the most important in Nigeria's struggle to consolidate its fledgling democracy," said Dapo Oyewole, director of the Centre for African Policy and Peace Strategy (CAPPS).
"It sees a highly contentious shift of power from the north to the south, breaking the informal zoning rotational agreement between these two regions that have competed for power since independence," he said.
Twenty of the 27 PDP state governors have publicly said they will back Jonathan. Many of the delegates arriving for the convention said the same, but they were reluctant to go on the record and there is no way of telling whether they will ultimately do so at a secret ballot.
Should Abubakar lose, he could form an alliance with a rival party and take northern support with him, going on to challenge Jonathan at the general elections.
SECURITY TIGHT
There was a carnival atmosphere -- albeit amid tight security -- as an estimated 5,000 delegates arrived at Eagle Square, a parade ground which has hosted national events in the two decades since the capital moved to Abuja from Lagos.
A band played and acrobats did cartwheels as helicopters buzzed overhead and the secret service, military and anti-riot police sealed off streets in a wide radius around the venue.
Africa's most populous nation is a patchwork of more than 200 ethnic groups, roughly equally divided between Christians and Muslims, who generally live peacefully side by side.
But regional and ethnic rivalries bubble under the surface and can easily be exploited by power-hungry politicians. The country has been rocked by violence in recent weeks.
Delegations from each of the 36 states will vote in turn in the middle of the open square, choosing between Jonathan, Abubakar, and veteran politician Sarah Jibril, the only female candidate and seen as a rank outsider.
A simple majority wins and results are expected in the early hours of Friday.
Nigeria has been rocked by violence as the election season gets underway, unrest which Jonathan's supporters suspect has been orchestrated to undermine his credibility.
A New Year's Eve bomb in Abuja killed four people. A series of blasts and subsequent clashes have killed more than 80 in the central city of Jos, the scene of frequent bursts of ethnic and religious unrest.
There has also been violence at political rallies in the Niger Delta, the heartland of Africa's biggest oil and gas industry. Jonathan is the first head of state from the restive region and some fear a backlash there if he loses.
The stakes in Thursday's vote are high and the outcome far from certain. But few expect the country to tumble into chaos.
"Nigeria has this inexplicable capacity to totter on the tip of anarchy, but fall back into an unexpected order of sorts," said Oyewole from CAPPS.
