The Covid-19 pandemic triggered polarisation across Europe. While most citizens supported governments’ containment measures, others took to the streets and voiced their dissatisfaction. The article focuses on the mobilisation potential related to this heterogenous protest wave. It examines individuals that show sympathy and are willing to engage in anti-containment demonstrations based on 16 waves of a rolling cross-section survey fielded in Germany in 2020/2021. The results show a considerable and stable mobilisation potential: every fifth respondent sympathises with the protesters, and around 60% of those are ready to participate themselves. Political distrust, far-right orientations and an emerging ‘freedom divide’ structure the potential, as do Covid-19-related economic and health threats. Moreover, the findings indicate a radicalisation process and show how ideology and threat perceptions drive the step from sympathy to willingness to participate, suggesting that ideological polarisation may quickly spill over to the streets given an appropriate supply of protest opportunities.