Health care was rated one of the key issues for voters in the 2018 midterm elections, according to exit polls. The election results set the stage for as many as 500 000 low-income individuals in the United States to gain coverage through new state Medicaid expansions under the Affordable Care Act (ACA). Expansion could occur in 5 additional states: 3 through ballot measures (Idaho, Nebraska, and Utah) and 2 through the election of new governors supportive of expansion (Kansas and Maine). If all 5 states expand Medicaid, this will bring the number of expansion states to 37 (plus Washington, DC), with a potential increase in Medicaid enrollees from approximately 50 million in 2010 prior to enactment of the ACA to a projected 76 million by 2020 (Figure and eFigure in the Supplement). The election also brings some short-term legislative certainty for the ACA, as the new Democratic majority in the House of Representatives will forestall further attempts to repeal the law for at least 2 years. In this Viewpoint, we provide a postelection update on the status of the Medicaid expansion and recent research on the ongoing effects of the law.