By Tom Ashby LAGOS, April 4 (Reuters) - Two front-runners have emerged as Nigeria approaches landmark elections this month despite mounting political violence and uncertainty over candidates, analysts and diplomats said on Wednesday. Two separate court rulings on Tuesday failed to resolve uncertainty over the candidacy of Vice President Atiku Abubakar, but analysts say he is fast losing relevance to the poll, which is turning into a straight contest between the ruling party's Umaru Yar'Adua and former army strongman Muhammadu Buhari. The elections on April 14 and 21 are a test for the survival of democracy in Africa's most populous nation and top oil producer, where power has more often changed hands by military coups in the 47 years since independence from Britain. Abubakar has been disqualified for a fraud indictment and is fighting a court battle against the clock to get his name back on the ballot. "If Abubakar does not run, it makes Buhari a rallying point for forces of opposition. It makes him a more formidable candidate. It makes for a more interesting election," said Bolaji Akinyemi, a former foreign minister, academic and lawyer. "But I am alarmed that weeks before the start of elections there is still a cloud of uncertainty over who the critical candidates will be," he added. Two separate courts issued apparently conflicting judgments on Abubakar's candidacy on Tuesday and the matter is now heading to the Supreme Court. It is unclear if it will deliver a judgment in time for the presidential vote on April 21. Even if Abubakar gets on the ballot at the last minute, his support is ebbing, analysts say. Some legal experts think he could even try to nullify the election after it is over if he is vindicated in a subsequent ruling, but legal opinion is divided on that point. TIMETABLE Voting will start on April 14, when Nigerians choose state governors and state house of assembly members. Elections for president and the National Assembly should follow a week later. The presidential poll could go into a run-off if no clear winner emerges in the first round. President Olusegun Obasanjo is constitutionally required to hand over on May 29, which would mark the first time one elected leader hands power to another. The ruling People Democratic Party's Yar'Adua, who has campaigned for extending Obasanjo's free-market reforms, is a little-known state governor who will rely on the party's control of over 28 of the 36 states to deliver votes. Buhari, whose 20-month army regime in the early 1980s featured austerity measures and tough punishments for crime and corruption, is a household name whose support is rooted in widespread disaffection with unemployment, poverty and crime. Civil society groups say preparations for the vote have been poor and rising political violence is going unchecked. More than 70 people have been killed in political violence in the last five months, according to the Nigerian press, and the violence is intensifying. "It seems plain that this April, Nigerian voters will again face the threat of violence, intimidation and fraud," said Peter Takirambudde, Africa director at Human Rights Watch. Buhari lost against Obasanjo in 2003 elections, but spent the next two years contesting the result in court until the Supreme Court ruled in Obasanjo's favour in 2005. The retired general says he has set up a relay system to monitor results this time, and many believe he will call for mass protests if he is dissatisfied with the result.
