President-elect Moon has gained office riding a wave of demand for social justice and a reform of democratic governance in South Korea. These are the issues that are certain to consume his attention and that of voters. U.S. policymakers need to be mindful that the domestic factors that led to this shift in power in South Korea will remain paramount. That said, the return to power of South Korea’s progressives augurs a significant shift in several areas of policy that will have a clear impact on alliance relations with the United States.