This article deploys a discursive–material analytical framework to trace how perceptions of data power are constructed in urban activist circles against data’s capacity to advance grassroots political goals. By framing South African data activism practices as a form of technopolitics—a concept that foregrounds the coconstitution of politics and technology through their anchoring to normative discourses—this analysis identifies how data are enrolled to substantiate a grassroots political discourse of spatial injustice yet how, through contestation by government officials, the fragility of data as objects of grassroots political power is laid bare. This empirical study of service provision social audits in Johannesburg and Cape Town shows how governments have effectively resisted their findings by singling out the quantitative data as a weak actor, exploiting this as an opportunity to advance their own political discourse of responsibility around service provision. In revealing how grassroots power was eventually strengthened through a strategic redistribution of agencies, the article then advances a nondeterministic understanding of data power and agency as relational, partial, and provisional and enacted through the coconstitution of people, technologies, and discourses, which might resonate with other examples of data activism and further urban data assemblages. These findings add empirical weight to claims of empowerment made in the emerging fields of data activism and data justice, and they raise further important questions for geographers and others interested in the ways in which data are enrolled to enact grassroots politics, as well as the discursive–material dimensions of urban technopolitics more generally. Key Words: data determinism, data imaginary, data justice, spatial justice, technopolitics.

本文采用了一种话语-材料分析框架，以追踪在城市维权人士圈子中如何构建对数据力量的认识，以及数据对推动基层政治目标的能力。通过将南非数据行动主义构筑为一种技术政治形式（通过将其固定在规范性话语中来凸显政治和技术的共存的概念），此分析确定了如何注册数据以证实空间不公正的基层政治话语。然而，如何通过政府官员的争夺来揭露作为基层政治权力对象的数据的脆弱性。这项对约翰内斯堡和开普敦服务提供社会审计的实证研究表明，政府如何通过挑选量化数据作为弱者来有效地抵制其发现，并以此为契机来推进自己围绕服务提供的政治责任论述。在揭示如何通过代理机构的战略性重新分配最终增强基层力量时，文章进而对数据权力和代理机构是关系，部分和临时的，并通过人员，技术和话语的联合制定而形成的不确定性理解，这可能会与数据行动主义的其他示例以及进一步的城市数据组合产生共鸣。这些发现增加了在数据行动主义和数据正义等新兴领域提出的权力主张的经验性权重，并且对地理学家和其他对数据注册方式以制定基层政治以及采取话语权感兴趣的人提出了进一步的重要问题。 –更普遍地讲城市技术政治的物质层面。关键词：数据确定性，数据虚构性，数据正义，空间正义，技术政治。