Global investment in stablecoins, a type of cryptocurrency designed to have a stable value relative to something else, has skyrocketed recently.1 While this growth raises questions about stablecoins’ relationship to the financial regulatory perimeter, 2 the near term will probably see federal regulators’ stated appetite for policy action exceed coordinated regulatory innovation. The example of the 1970s policy response to money market funds (MMFs)3 has parallels to stablecoins’ potential emergence as private digital money. As was the case with 1970s MMFs, the SEC will likely be stablecoins’ leading federal supervisor but will face substantial constraints on its oversight and limited help from other regulators.