S.D. Codified Laws § 2-9-2
The Legislative Research Council shall have an executive board, to be known as the Executive Board of the Legislative Research Council, which shall consist of fifteen members, as follows: four members from the Senate and five members from the House of Representatives, to be elected by a majority vote by their respective legislative bodies in party caucus before each regular session of the Legislature held in odd-numbered years, and ex officio the president pro tempore, majority leader, and minority leader of the Senate and the speaker, majority leader, and minority leader of the House of Representatives elected in such regular session. The number of senate and house members on the executive board shall remain constant, and any vacancy occurring shall be filled by the respective legislative bodies in party caucus. If a vacancy occurs in the ex officio position on the board for the president pro tempore, the vacancy on the board shall be filled by the majority party caucus until the Senate elects a new president pro tempore. If a vacancy occurs in the ex officio position on the board for the speaker, the vacancy on the board shall be filled by the speaker pro tempore until the House of Representatives elects a new speaker. No board member, excepting ex officio, may serve more than three successive terms.
SDCL 2-9-2