This research note provides a detailed account of the development and implementation of a household survey conducted in 2016 as part of a larger investigation into the lifeways and political subjectivities of Brazil’s “once-rising poor,” the demographic sector comprising poor and working-class people who experienced various forms of socioeconomic mobility in the early twenty-first century. After reflecting on the challenges of maintaining a critical perspective on class labels and relations that were intensely contested at the time, the article introduces the survey sample (n = 1,204), highlighting variables captured. It then establishes the demographic profile, mobility experiences, political values, attitudes, and behaviors of the sample. The portrait that emerges for this sector is one of economic precarity, heterogeneous experiences of socioeconomic mobility (and nonmobility) over the past two decades, and significant alienation from formal politics.