Interest groups capitalize on the opportunity to influence salient U.S. Supreme Court confirmations, while pursuing organizational and policy goals and hoping to mobilize the public. We test the opportunities and limits of ad influence on political mobilization specifically looking at calls to action (i.e., donations, contacting senators, and social media engagement). By analyzing responses to real interest group-produced video ads from Amy Coney Barrett’s and Ketanji Brown Jackson’s nominations, we discover ads can potentially influence individuals’ political behavior online and spur offline political engagement. Specifically, we find name recognition, partisan congruence, and positive tone positively influence respondent engagement in calls to action. We find ad format in terms of forced exposure and negative tone decrease engagement likelihood. Our study contributes novel insights into the role of online advertising in shaping political behavior around nominations in the digital age.