This essay suggests a theory of strategic legislative agenda control. It argues that a single party can effectively set the agenda under majoritarian gatekeeping rules without obtaining majority or even plurality status. The agenda-setting party need not be the median party in the assembly nor supported by executive-led parliamentary coalitions. The Mexican Chamber of Deputies provides a case study of how majoritarian gatekeeping and political context establish the conditions necessary for one-party-led agenda-setting in a fragmented congress with or without enduring coalitions. The failure of opposition coalitions to roll the ‘Partido Revolucionario Institucional’ evinces that party's ability to set the agenda through strategic coalition formation since 2000. High levels of party unity combined with strategic positioning have allowed the PRI to do so. The strategic nature of the PRI's coalition-making is documented and analyzed in the context of its historically pragmatic approach to coalition-making. The argument is supported by roll-call data analysis, using WNOMINATE, WRice scores, and roll rates.
