The vice president of the United States (VP or VPOTUS) is the second-highest officer in the executive branch of the U.S. federal government, after the president of the United States, and ranks first in the presidential line of succession. The vice president is also an officer in the legislative branch, as president of the Senate. In this capacity, the vice president is empowered to preside over Senate deliberations, but may not vote except to cast a tie-breaking vote. The vice president also presides over joint sessions of Congress.
The vice president is indirectly elected together with the president to a four-year term of office by the people of the United States through the Electoral College. Section 2 of the Twenty-fifth Amendment, ratified in 1967, created a mechanism for intra-term vice presidential succession, establishing that vice presidential vacancies will be filled by the president and confirmed by both houses of Congress. Previously, whenever a vice president had succeeded to the presidency or had died or resigned from office, the vice presidency remained vacant until the next presidential and vice presidential terms began.
The vice president is also a statutory member of the National Security Council, and the Board of Regents of the Smithsonian Institution. The Office of the Vice President assists and organises the vice president's official functions. The role of the vice presidency has changed dramatically since the office was created during the 1787 constitutional Convention. Especially over the past 100 years, the vice presidency has evolved into a position of domestic and foreign policy political power, and is now widely seen as an integral part of a president's administration. As the vice president's role within the executive branch has expanded, his role within the legislative branch has contracted; for example, he presides over the Senate only infrequently.
The Constitution does not expressly assign the vice presidency to any one branch, causing a dispute among scholars about which branch of government the office belongs to: 1) the executive branch; 2) the legislative branch; 3) both; or 4) neither. The modern view of the vice president as an officer of the executive branch (isolated almost totally from the legislative branch) is due in large part to the assignment of executive authority to the vice president by either the president or Congress.