The essay analyzes the 2017 anticorruption protests in Romania by implementing and complementing the scholarship on political opportunity structures and civil mobilization. It argues that corruption allegations and corruption investigations are inherently open to politicization and shrouded in uncertainty, which substantially raises the cost of understanding the corruption milieu. This uncertainty arises because (1) it is hard to establish whether the corruption act has occurred; (2) there is no agreement how to ensure the independence of the prosecutor; (3) there is lack of clarity concerning who can strip alleged officials of immunity, and (4) it is unclear how information collected by the secret service should be utilized. Three elements of the political opportunity structure shaped the cost-benefit calculus of potential protesters in Romania in 2017 and served as "virtual markers" of certainty. The dual executive standoff between the president and the government raised the benefits of protesting, while the communist cleavage and the outspoken personalities of Presidents Basescu and Iohannis served as virtual markers of certainty that decreased the cost of figuring out the complex corruption narrative and spurred the protests.