This article analyzes how uncertainty about the location of the pivotal actor influences the outcome of Commission proposals. We argue that the Commission is an imperfect agenda-setter and expect that Commission proposals are more likely to fail when uncertainty increases in the bicameral legislature of the Council and the European Parliament. Considering all legislative acts decided under the co-decision procedure proposed in the period from November 1993 until December 2009, we focus on withdrawal of Commission proposals as failures. In the empirical analysis we distinguish between electoral and procedural uncertainty and provide evidence that both types of uncertainty explain withdrawal of Commission proposals.