Well-financed opposition parties can exert their organizational strength to undercut the territorial advantages of political machines and clientele networks. In the first decade of the twenty-first century, leftist parties in Brazil's Northeast region brought conservative dominance to an end. The Workers' Party (Partido dos Trabalhadores, PT) led this shift, not only garnering regional majorities in presidential elections but also winning multiple governorships and increasing its share of federal and state legislative seats in the region. In contrast to arguments attributing recent electoral shifts in the Northeast to civil society, aggregate growth, and conditional cash transfers, we argue that the territorial expansion of the PT organization played a central role. A spike in party finances between 2001 and 2003 enabled the PT, for the first time, to establish party offices in northeastern municipalities from the top down. Drawing from underutilized data and sources, we show that the PT leadership eroded conservatives' monopoly on rural territory in the Northeast by strategically targeting hundreds of conservative-dominated municipalities and investing resources to stimulate the formation of local offices. The study demonstrates that this top-down territorial targeting produced considerable electoral gains for PT candidates across federal and state races.