According to the SD Constitution1 it now takes a simple majority of South Dakota voters to change a law or amend the constitution. South Dakotans can make changes with a ballot measure – referring a law, initiating a new law or amending the constitution.
Senate Joint Resolution 2 (SJR2) proposed a state-wide vote to change the constitution’s simple majority requirement to a supermajority (two-thirds of voters) to pass initiated measures2 or constitutional amendments3 “that have the effect of increasing the rate of taxation by the state.”4 When a vote requires a supermajority to pass, the minority of voters (1 of 3) effectively control the outcome of the election.
SJR2 was amended by and passed out of Senate Tax Committee on 1-25-13 with a 6-1 vote, passed the Senate by a vote of 25 to 10 , passed the House Judiciary Committee on 2-4-13 with a 8-4  vote but was ultimated defeated in the house both on initial vote 34-35 and reconsideration 32-35 .
Joint Resolutions require only a simple majority to pass each house and do not require a governor’s signature. Had it passed and been placed on 2014 SD ballot, a simple majority vote of the people would have been required to pass the constitutional amendment, restricting future measures from 2016 forward to a two-thirds majority vote.
According to the office of the SD Secretary of State,5 there are no other portions of the constitution that require a two-thirds majority vote for amendment. SJR2 language also requires a super-majority to “further amend this [new] section of the Constitution.”
South Dakota was the first state to adopt initiative and referendum on a statewide level and did so in 1898.6 The simple majority ratification criteria has been part of the SD constitution for 115 years.
See previously published SD B&PP descriptive research on Ballot Measures in South Dakota. 
1SD Constitution Article XI, §13 and Article XXIII § 3
2SD Constitution Article XI, section 13 – proposed change increases from simple majority to “consent of a two-thirds vote of the people in exercise of their right of initiative to change the rate of taxation imposed by the state of South Dakota on personal,or corporate income or on sales or services, or the allowable levies of the percentage basis for determining valuation as fixed by law for purposes of taxation on real or personal property.
3SD Constitution Article XI NEW SECTION 16 includes statement “any amendment to this constitution that has the effect of increasing the rate of taxation by the state or that has the effect of imposing any new tax, or that has the effect of extending the imposition of a tax beyond the defined period of time for which it was imposed, or that further amends this section of the Constitution, is deemed to be approved by the people only by consent of a two-thirds vote of the people.
4The Title of Senate Joint Resolution 2 is: Proposing and submitting to the electors at the next general election amendments to Article XI of the constitution of the State of South Dakota, relating to the vote required to increase taxes.
5Consultation with SD Secretary of State office 2-12-13.
6Initiative & Referendum Institute at the University of Southern California. http://www.iandrinstitute.org/South%20Dakota.htm  See David Schmidt, Citizen Lawmakers: The Ballot Initiative Revolution (Temple University Press, 1989).