In a presidential system, the citizens elect the members of the legislature and the chief executive known as the president. The president serves as head of state, runs the government on a day-to-day basis, and heads the military. However, the president does not make the laws. The legislature has the job of making the laws. The president serves for a fixed amount of time; then elections are held again. The legislature does not have the power to force an early election, and the president does not have the power to dissolve the legislature. The United States, Mexico and most South American countries have presidential democracies.