This article offers an empirical test of why some legislators’ bills are more likely to move forward in the legislative process. We argue that who signs the bill matters when it comes to the level of support that the proposal receives. Successful bills will be sponsored by a greater number of members ( bandwagon factor) and political adversaries ( support across the aisle factor). On the contrary, failed initiatives will be those sponsored by inexperienced parliamentarians ( newcomers factor). We examine the case of Chile and test the expectations with legislative data on parliamentarians’ bills.