The Power of Opposition: Legislative Effectiveness in Mexico's Multiparty Democracy develops a theory of legislative effectiveness in presidential systems where it is rare for presidents to control a majority of seats in the legislature. Legislators belonging to the president's party are often constrained in their behavior as the executive branch has an overarching interest in ensuring copartisan legislative proposals fit within the president's agenda. Executive bills often require bargains with the opposition to secure votes, and legislators from the president's party may find their bills coopted by the president, or blocked if they conflict with presidential priorities. As a result, legislators from governing parties are generally less effective when it comes to their own initiatives. Presidents allow the opposition to push their own priorities through the legislative process, or provide credit-claiming opportunities on major presidential initiatives. Since opposition legislators can exchange votes on executive bills for presidential support on opposition-led initiatives, they are generally more effective at navigating their own proposals through the legislative process. Yann P. Kerevel and Sergio A. Bárcena Juárez demonstrate support for this argument drawing on extensive quantitative data from Mexico's Chamber of Deputies from 1997-2024, and interviews with numerous lawmakers and staffers.

Yann P. Kerevel is professor of political science at Louisiana State University. His research examines the effects of political institutions on legislative behavior, and the extent to which the background characteristics of legislators shape how they represent citizens.

Sergio A. Bárcena Juárez is full-time researcher at Mexicös Tecnológico de Monterrey, in the Humanities and Education department. His research mainly focuses on Mexican legislative politics, the institutionalization of legislatures and issues of AI usage in parliaments as well as its effects on political representation.