The single slate by the NBDC is called for by Article XII, Section 9 of the GSUSA Constitution, which states: “The committee shall present at each regular session of the National Council a single slate of nominees for: a) the President; b) the Vice Presidents; c) the Secretary; d) the Treasurer; e) members‐at‐large of the National Board of Directors; and f) members of the National Board Development Committee. No member of the National Board Development Committee shall be eligible to be nominated for any officer position. A nominee for President shall be a current member of the National Board of Directors.”
Also, in Robert’s Rules, 12th edition (see 46:11), it says, “It is usually not sound to require the committee to nominate more than one candidate for each office, since the committee can easily circumvent such a provision by nominating only one person who has any chance of being elected.” If the National Council doesn’t like the slate presented, it has the power to make nominations from the floor for any position provided that notice is given to the President and the Chair of the National Board Development Committee at least 48 hours prior to the Session starting.
Source: 2017 Board Slate Frequently Asked Questions and Constitution/ARTICLE XII NATIONAL BOARD DEVELOPMENT COMMITTEE, NOMINATIONS, AND ELECTIONS/Nominations