Ahead of the general election of 2015, a merger of the biggest opposition parties – the Action Congress of Nigeria, the Congress for Progressive Change, the All Nigeria Peoples Party (a faction of the All Progressives Grand Alliance), and the new PDP (a faction of serving governors of the ruling People's Democratic Party) – formed the All Progressives Congress. In the 2015 presidential election, former military head of state General Muhammadu Buhari – who had previously contested in the 2003, 2007, and 2011 presidential elections—defeated incumbent Jonathan of the People's Democratic Party by over two million votes, ending the party's sixteen-year rule in the country and marking the first time in the history of Nigeria that an incumbent president lost to an opposition candidate. Observers generally praised the election as being fair. Jonathan was generally praised for conceding defeat and limiting the risk of unrest. In the 2019 presidential election, Buhari was re-elected for a second term in office defeating his closet rival Atiku Abubakar.