The duties of the vice president of the United States are specified in Article 1 of the U.S. Constitution. The VP formally acts as the president of the United States Senate. In reality, the VP does not hold actual executive power in the Senate, except for the ability to cast tie votes. United States Senate: Vice President of the United States
History
The vice president's traditional duties has changed over the years due to cultural, not legislative, changes. In the past, the vice president held more actual power over the Senate. The VP became more closely involved with the administration of the president in the 20th Century. United States Senate: Vice President of the United States
Sarah Palin on Role of VP
Sarah Palin made headlines in October 2008 when she explained the duties of the vice president to a 7-year old boy in a TV interview. Palin said to the boy that the vice president is "in charge of the Senate". In reality, however, the president does not have any executive power in the Senate. She was criticized in the media for her comment.ABC News: Palin Says Vice President "In Charge Of" Senate (October 22, 2008)