Simplified Rules of Order
Procedures Used in Meetings
Voting Rights of the Chair
Robert's rules state that if the presiding officer is a member of the group concerned, he or she has the same voting rights as any other member. The chair protects impartiality by exercising voting rights only when his or her vote would affect the outcome. In such cases the chair can either vote and thereby change the result, or can abstain. If the chair abstains, he/she announces the result of the vote with no mention of his/her own vote.
The outcome of any motion requiring a majority vote will be determined by the chair's action in cases in which, without his/her vote, there is either a tie vote or one more vote in the affirmative than in the negative. Because a majority of affirmative votes is necessary to adopt a motion, a tie vote rejects the motion. If there is a tie without the chair's vote, the chair can vote in the affirmative, thereby creating a majority for the motion. If the chair abstains from voting in such a case, however, the motion is lost (because it did not receive a majority).
If there is one more affirmative vote than negative votes without the chair's vote, the motion is adopted if the chair abstains. If he/she votes in the negative, however, the result is a tie and the motion is therefore lost.
In short, the chairperson can vote either to break or to cause a tie; or, when a two-thirds vote is required, can vote either to cause or to block the attainment of the necessary two-thirds.
The chair cannot vote twice, once as a member, then again in his/her capacity as presiding officer.