Voting by President and Deputy President
The President and Deputy President are in all cases entitled to a vote. When in the chair they may vote by stating to the tellers whether they vote with the “Ayes” or with the “Noes”.[51]
Voting by the President, or the Deputy President as Chair of Committees, when in the chair, is optional.[52] In practice this rule is extended to any senator occupying the chair. The reason for the rule is that a senator in the chair cannot avoid voting by leaving the chamber when a division is called for, as can other senators. In practice, however, the senator in the chair normally votes in a division.
When the President is present in committee of the whole during a division the President must vote. Similarly, if the Deputy President is present in the Senate when a division is presided over by the President, the Deputy President must vote.
As with the President, a senator in the chair has a deliberative vote and not a casting or deciding vote.