As global programs for HIV response look to transfer responsibility and financing increasingly to country governments, the political will to take on these responsibilities becomes increasingly prominent. However, defining and assessing political will are problematic; it involves intent and motivation, and thus is inherently difficult to observe. It is intimately connected to capacity and is contextually embedded. This article describes an operational model of political will comprised of seven components that are observable and measurable. Two case studies illustrate the application of the model and shed light on the interconnections among commitment, capacity and context: South Africa and China. Strategy options to build political will for HIV response identify possible actions for both government and civil society. Political will as a concept is most usefully viewed as integrated within larger political and bureaucratic processes, as a product of the complex array of incentives and disincentives that those processes create. However, this conclusion is not a recipe for discouragement or inaction. Agent‐based conceptualizations of policy change offer a solid grounding for building political will that supports HIV policy and programs. Copyright © 2015 John Wiley & Sons, Ltd.