Former Nigerian president Olusegun Obasanjo has endorsed opposition candidate and former military ruler Muhammadu Buhari to be the next leader of Africa’s most populous nation. In a bid to oust incumbent Goodluck Jonathan, Obasanjo also warned the government not to give the military an opportunity to return to power.

The endorsement, in an interview with the Financial Times, is unusual for one reason. Obasanjo is a founding member of president Jonathan’s People’s Democratic Party. Buhari is leader of the opposition All Progressives Congress. Obasanjo was at one time considered something of a political mentor to Jonathan, who he plucked out of political obscurity to the role of vice-president in 2007. But the two have fallen out in recent years, as the 77-year old former president has become increasingly critical of Jonathan’s government.

In what is seen as a very close election, an open endorsement by Obasanjo could help win Buhari some meaningful votes. Obasanjo, a former military ruler before turning to politics, defended Buhari’s harsh but short period as a military ruler in the 1980s.

“The circumstances [Buhari] will be working under if he wins the election are different from the one he worked under before, where he was both the executive and the legislature — he knows that,” said Obasanjo. “He’s smart enough. He’s educated enough. He’s experienced enough. Why shouldn’t I support him?”

In the meantime, the country remains on tenterhooks after the independent electoral commission delayed the elections for six weeks until Mar. 28. That came after warnings by the military that it could not guarantee security, particularly in the country’s northeast region, which is currently under frequent attack from Boko Haram insurgents. When the delay was announced last weekend, the head of Nigeria’s independent election committee, INEC, made clear that he felt his hands were tied by the military and security advice he had received.

Many Nigerian commentators believe Jonathan’s government, which is facing its closest-ever elections, used the military to engineer the delay. Obasanjo’s concern is that postponing elections because of an unpredictable security situation could lead to further delays. If a new government is not sworn in by May 29, it would trigger a constitutional impasse, allowing the military to take control via an interim government.

The uncertainty has led to speculation and rumors in Nigeria that the military, which has ruled the country for more than half of its 54 years since independence, will make an unwelcome return. Obasanjo also addressed this with the FT.

“I sincerely hope that the president is not going for broke and saying ‘look dammit, it’s either I have it or nobody has it’. I hope that we will not have a coup . . . I hope we can avoid it.”