How does strategic capacity affect political activism of advocacy organizations (interest groups, trade unions, social movement organizations)? Classical theories tend to treat advocacy organizations as passive subjects that are shaped by political context, financial donors or availability of membership. However, advocacy organizations also have a strategic capacity to actively decide on their goals and political actions. Skilled leaders or effective coordination and decision-making practices are important factors because they develop and employ heuristics, motivation, knowledge, and skills that help effectively meet the goals of the organization. Importantly, strategic capacity should be also able to compensate for the lack of other factors that support activism (resources or facilitative context) and thus enable political mobilization also for organizations that are small, poor on resources and face adversarial environment. This paper further develops the theory of organizational strategic capacity (Ganz et al.) and tests it on survey data from around 200 Czech advocacy organizations (snowball sample of advocacy organizations in seven issue industries). Czechia is a typical case that should show a strong role of strategic capacity as other facilitative factors of political advocacy (organizational and financial resources, supportive environment) are relatively very low here and many organizations in the country rely on a “transactional activism” (networking among smaller organizations). The article conceptualizes “transactional activism” as a form of organizational strategic capacity and tests the direct effect of several strategic capacity factors (leadership skills, inter-organizational networks, openness of decision-making processes, decentralized organizational structure) on organizations’ political advocacy (lobbying, media campaigning, grass-roots activism) and their conditioning effect on the influence of material and human resources and perceived openness of political opportunities.