This paper explores how external actors promote democratization in contentious environments by examining the US response to the Arab Spring in Tunisia between 2011 and 2014. The removal of Ben Ali in Tunisia in 2011 and the subsequent transition to democracy in that country took US policy makers by surprise. Given the lack of credibility of the US as a democracy promoter in the region, the US pursued a cautious strategy in encouraging Tunisias transition. As a result, it failed to capitalize on the opportunity to create a positive feedback loop that could have supported Tunisias democratic transition. This case illustrates the importance of credibility to successful democracy promotion by external actors and highlights the need for further research in this area.