While complementary in many ways, the cartel and the conditional party government (CPG) theories of legislative party power have disparate expectations for the stability of the majority party’s negative agenda control. Cartel theorists contend that negative agenda control is relatively constant over time, while CPG proponents suggest that this type of veto power varies with intra-party preference cohesion and inter-party preference distinction. In this article, we enter this debate by considering an alternative and under-explored indicator of negative agenda control: participation in discharge petition efforts. Our findings demonstrate the instability of the majority party’s ability to control discharge efforts, with majority party (co)sponsors showing a significantly greater likelihood of ‘waffling’ during periods of stronger party unity and more vigorous leadership power.