A presidential system separates the executive, legislative, judicial functions of the government and provides what are commonly called checks and balances to limit the governmental powers and guarantee liberties and rights. is it really like that? Most presidents in Latin America and in Africa enjoy absolute power and disallow any political opposition. But significantly, the dominant tendency of American constitutional history has been to concentrate power in the executive branch. There was an inevitability about the expansion of presidential power. In the light of the nature of the executive power, the President can act unilaterally and quickly without the collaboration of the other branches. Futhermore, the power he exercises, such as the veto power and the pardon power may be used to defense usurpations by the other branches. Matters are different in the legislative and judicial branches. They operate under majority rule. Also, to fulfill their acts, it is necessary to obtain the assistance of the executive branch. In short, rapid action is alien to the nature of the legislative and judicial power. Although the Presidential constitutional powers are extensive, it doesn`t justify the abuse of Presidential power. Instead, the aim of ascertaining the supremacy of presidential power is to puts emphasis on the controlling the presidential powers by the other branches.