Does plausible deniability work? Assessing the effectiveness of unclaimed coercive acts in the Ukraine war

States conduct unclaimed coercive acts, imposing costs on adversaries to signal resolve but denying (or not claiming) responsibility. Some scholars posit that unclaimed acts have considerable potential to coerce targets, while containing escalation risks. Others suggest that unclaimed coercive efforts tend to fail and trigger escalation. We assess these competing perspectives about the effects of unclaimed attacks with a vignette experiment exposing US-based respondents to a scenario where, after Russia warns of unpredictable consequences if NATO continues providing weapons to Ukraine, an explosion occurs at a NATO base in Poland used to funnel weapons to Ukraine. Intelligence agencies and independent analysts identify Russia as the likely culprit, while not ruling out the possibility of an accident. We randomize whether Russia claimed or denied responsibility for the explosion and find that unclaimed acts have lower coercive leverage than claimed ones, but the two do not significantly differ in escalation risk.