South Dakota voters have approved the expansion of Medicaid health insurance to tens of thousands of low-income residents through a constitutional amendment. South Dakota is the 39th state to expand eligibility for the government health insurance program under the Affordable Care Act. The amendment will extend Medicaid to those earning up to 138% of the federal poverty level — currently about $18,800 for an individual or $38,300 for a family of four. The Republican-controlled Legislature had long resisted expanding Medicaid eligibility, and GOP Gov. Kristi Noem opposed it. But a coalition of South Dakota health care groups and progressive organizations backed a well-funded ballot campaign this year.