Plurality-led congresses are among the most pervasive and least studied phenomena in presidential systems around the world. Often conflated with divided government, where an organized opposition controls a majority of seats in congress, plurality-led congresses are characterized by a party with fewer than fifty percent of the seats still in control of the legislative gates. Extensive gatekeeping authority without plenary majorities, this book shows, leads to policy outcomes that are substantially different from those observed in majority-led congresses. Through detailed analyses of legislative success in Argentina and Uruguay, this book explores the determinants of law enactment in fragmented congresses. It describes in detail how the lack of majority support explains legislative success in standing committees, the chamber directorate, and on the plenary floor.