Nigeria is a Federal Republic modelled after the United States, with executive power exercised by the president. It is influenced by the Westminster System model[citation needed] in the composition and management of the upper and lower houses of the bicameral legislature. The president presides as both Head of State and head of the national executive; the leader is elected by popular vote to a maximum of two 4-year terms. In the March 28, 2015 presidential election, General Muhammadu Buhari emerged victorious to become the Federal President of Nigeria, defeating then incumbent Goodluck Jonathan.