The only regular responsibility that the Constitutional Convention assigned to the office of the Vice President (other than the duty to receive the tally of electoral votes for President) was to preside over the Senate and to cast tie-breaking votes. Because this role seemed to give the Vice President some legislative responsibility, George Mason argued during the Convention that this was a violation of the separation of powers, that “it mixed too much” the executive and legislative powers. But Roger Sherman responded: “If the Vice President were not to be President of the Senate, he would be without employment.” The Anti-Federalists echoed Mason’s concern, that the Vice President would be an agent of executive subversion of the legislature. John Adams intentionally signed Senate documents as “John Adams, Vice President.” The Anti-Federalist William Maclay responded, “Sir, we know you not as Vice President within this House. As President of the Senate only do we know you, as President of the Senate only can you sign or authenticate any Act of that Body.”

Allowing the Vice President to preside over the Senate, and to vote in case of a tie, solved two important problems. First, it allowed that body—at all times—to come to a definitive resolution, because the President of the Senate would break tie votes. Second, it preserved the equality of the states in the Senate. As Justice Joseph Story noted in his Commentaries on the Constitution of the United States (1833), should a Senator have been chosen to preside over the body, and should that Senator cast the tie-breaking vote, a state would, in effect, increase its representation.

Alternatively, if the Senator as presiding President would be allowed to vote only in case of a tie, a state would end up losing half its representation during normal votes. The Federalist No. 68. There have been over two hundred occasions when the Vice President has had to cast a tie-breaking vote, but most occurred early in the history of the Republic. In fact, the first Vice President, John Adams, cast the highest number of such votes, twenty-nine in all, including the Decision of 1789, confirming the President’s authority to remove executive officers.

Early in the Republic the Vice President took seriously his constitutional duty of presiding over the Senate, and John Adams and Thomas Jefferson did much to shape the presider’s role. Rarely, however, does the Vice President sit in modern times. The President Pro Tempore of the Senate is the formal substitute, but normally a junior Member of the Senate is assigned to sit in the chair. The ambiguity in the constitutional position of the Vice President has led to a debate among commentators as to whether to site the office in the legislative or executive branches. The consensus among the Framers seems to have been that his constitutional duties lay in the legislative branch unless and until he succeeded to the Presidency. Significantly, the Vice President’s salary, his expenses, and his staff are still paid for out of the Senate’s budget. Nonetheless, under the broad discretion that the Constitution leaves to each branch to develop its own structure, the political influence of Vice Presidents in the executive branch has increased as modern Presidents have delegated many functions to their Vice Presidents.