The United States Electoral College is the institution that elects the President and Vice President of the United States every four years. Citizens of the United States do not directly elect the president or the vice president; instead, these voters directly elect designated intermediaries called "electors," who almost always have pledged to vote for particular presidential and vice presidential candidates (though unpledged electors are possible) and who are themselves selected according to the particular laws of each state. Electors are apportioned to each of the 50 states as well as to the District of Columbia (also known as Washington, D.C.). The number of electors in each state is equal to the number of members of Congress to which the state is entitled, while the Twenty-third Amendment grants the District of Columbia the same number of electors as the least populous state, currently three. Therefore, in total, there are currently 538 electors, corresponding to the 435 members of the House of Representatives and 100 senators, plus the three additional electors from the District of Columbia.