Have you ever watched the Senate during a very close vote? If so, you may have seen the vice president sitting or standing at the presiding officer's desk on the Senate Floor. Other than to succeed to the presidency upon the death or resignation of a president, a vice president's only constitutional duty is to preside over the Senate. Vice presidents cannot vote in the Senate, except to break a tie, nor may they formally address the Senate, except with the senators' permission. Initially vice presidents appointed senators to standing committees, regulated access to the galleries and supervised the keeping of the Senate Journal, but these duties were later removed.
During the twentieth and twenty-first centuries the vice president's role has evolved into more of an executive branch position, and is usually seen as an integral part of a president's administration. He presides over the Senate only on ceremonial occasions or when a tie-breaking vote may be needed.
When the vice president is absent, the president pro tempore presides over the Senate. Junior senators fill in as presiding officer when neither the vice president nor president pro tempore is on the Senate Floor.
To learn more about the vice president, president pro tempore, and other Senate leaders and officers visit the Virtual Reference Desk.