"Despite the far-reaching potential expansion of Medicaid under the [Affordable Care Act], our estimates demonstrate that a substantial portion of low-income uninsured adults will be ineligible for Medicaid because of their immigration status." That is a key finding of a new study by the Robert Wood Johnson Foundation, which highlights four states with high percentages of immigrants: Arizona , California , Nevada and Texas . In these states, the challenge of developing "strategies for meeting the health care needs of" immigrants will be "particularly difficult for safety-net providers in states with large numbers of immigrants who will not be eligible for Medicaid."