Minozzi and Volden advance the idea that a substantial portion of partisan voting activity in Congress is a simple call to unity that is especially easily embraced by ideological extremists. If correct, Minozzi and Volden’s findings should extend from the House to the Senate, despite differences in institutional structures and in tools at the disposal of party leaders across the two chambers. We adapt the theory and measurement of party calls to the Senate. In so doing, we find that both the House and the Senate have relied heavily (and increasingly) on party calls over the past four decades. In the Senate in particular, the lens of party calls opens new opportunities for scholars to explore partisan legislative behavior. We take advantage of one such opportunity to show how electoral concerns limit senators’ responsiveness to party calls, depriving party leaders of support for their agenda items.