This paper updates and extends the Political Market Framework (PMF) by integrating elements of interest groups and political market theory with policy entrepreneurs’ (PEs) roles in explaining the patterns of urban infrastructure construction. The prominent role of PEs is observed through a grounded analysis of two large infrastructure projects in Mexico City. A comparative study of the cases suggests that: (1) The agency of PEs in political markets is central to explaining the construction of urban infrastructure; (2) PEs contribute to the definition of pro-growth or anti-growth coalitions and the definition of public problems; (3) the legitimacy of PEs is grounded in their political or technical reputation, or both; (4) the appropriate use of political institutions requires that PEs know how to use electoral timing strategically; and (5) the role of PEs seems to be better understood within a bounded analysis framework, such as the political markets approach.