In the fourth part of this mini-series on single-payer systems, Suzanne Spradley and Chase Cannon look at four versions of single-payer system legislation introduced by the Democrats. The two walk through the four versions from least to most intrusive to the current system, which is based on employer-provided coverage. The four versions are a Medicaid buy-in (also called a “State Public Option”), Medicare buy-in (also called “Medicare for More”), Medicare-X Choice Act (which includes an expansion of the current premium tax credits administered through the state health insurance exchanges), and the full blown Bernie Sanders-style Medicare for All (true single payer, nationalized health care). Suzanne discusses the terminology, definition, structure, funding, provider impact, consequences, and potential challenges to each of the four versions. Suzanne and Chase conclude with a look at what all this could mean for the 2020 elections.