President-elect Trump and Republican leaders in Congress have vowed to repeal the Affordable Care Act (ACA) and replace it with an alternative plan. There are now 32 states (including DC) that have adopted the ACA’s Medicaid expansion. While the details of a repeal-and-replace plan are not yet available to assess its impact, a new brief reveals what’s potentially at stake for Medicaid in the debate by examining the changes in health coverage and financing that have occurred since the Medicaid expansion took effect in January 2014.

Key findings:

• By 2015, an estimated 11 million Medicaid enrollees nationally were adults who were made newly eligible by the expansion. They were part of a larger net increase in Medicaid enrollment since the implementation of the ACA.  (State-level Medicaid enrollment data as of 2015, including enrollment of those newly eligible in expansion states, is available in Appendix Table 2.)
• The Medicaid enrollment gains contributed to a big decline in the uninsured rate among nonelderly individuals in the U.S., which fell from 16.6 percent in 2013 to a historic low of 10 percent in 2016.
• Medicaid expansion states received $79 billion from January 2014 to June 2015 in new federal funding (with little or no state match) to help cover newly eligible enrollees. Under current law, federal funding will cover 95 percent of Medicaid expansion costs in 2017 and will phase down to 90 percent for 2020 and beyond.