Why states expand Medicaid: party, resources, and history.

After the passage of the Patient Protection and Affordable Care Act in March 2010 and the affirmation of its constitutionality by the Supreme Court in 2012, key decisions about the implementation of health care reform are now in the hands of states. But our understanding of these decisions is hampered by simplistic sortings of state directions into two or three simple, rigid categories. This article takes a different approach--it tracks the variations in relative state progress in implementing Medicaid expansion across a continuum of activities and steps in the decision-making process. This new measure reveals wide variation not only among states that have adopted Medicaid expansion but also among those that have rejected it but have also made progress. We use this new measure to spotlight cross-pressured Republican states that have adopted Medicaid expansion or have prepared to move forward and to explore possible explanations for implementation that extend beyond a simple focus on party control.