With the fall of Nigeria’s dictatorship and the introduction of democracy in 1999, governors in the mainly Muslim northern provinces believed they had struck a deal with their southern counterparts on a regional rotation of the country’s presidency. In 2007, arguing that it was their turn to choose a chief executive, they bitterly opposed a bid by then-President Olusegun Obasanjo, a southerner and a Christian, to rewrite Nigeria’s constitution in hopes of winning a third term.