OKLAHOMA CITY (AP) — Oklahoma voters narrowly decided on Tuesday to expand Medicaid health insurance to tens of thousands low-income residents, becoming the first state to amend its Constitution to do so.

With 100% of precincts reporting unofficial results, State Question 802 passed by less than 1 percentage point. The question fared well in metropolitan areas, including Oklahoma City and Tulsa, but was overwhelmingly opposed in rural counties.

Idaho, Maine, Nebraska and Utah have all expanded Medicaid through ballot questions, but did so by amending state statutes, according to the nonpartisa...