Social capital is still often presumed as having positive consequences for societies and communities, less benign aspects are frequently overlooked. Nevertheless, scholarship distinguishes between bridging and bonding social capital to mark that social ties might have very different effects. In this paper, we study the “darker sides” of social capital, arguing that to understand the mechanisms that may propel benign and less benign formations of social capital we need to analyze these variations in context. We focus on think tanks, i.e., policy advice institutions, who are often described as organizations bridging various social fields and brokering contacts between various individuals. We argue, however, that a sharply polarized context turns think tanks to bonding, rather than bridging institutions. Our data consists of 40 interviews with representatives from Polish think tanks, collected in two waves (in 2013 and in 2020/2021), which allows us to trace changes over time. Since the radical right wing Law and Justice came to power in 2015, Polish politics and society are deeply polarized along the axis of the socio-cultural dimension (for or against liberal democracy). The analysis indicates that the networks Polish think tanks use for their activities have transformed from bridging between various groups of organizations, to bonding between similar types of organizations.