<p>Drawing on theories of affective intelligence and intergroup emotions, we develop a theory of affective representation in Congress in which lawmakers vary the emotional tone of their communications to align with the emotional experiences of rank-and-file co-partisans, thereby strengthening their popularity with constituents. In a nationalized political environment where control of the presidency is crucial, belonging to the presidential party influences both the emotional experiences of rank-and-file partisans and the emotions lawmakers express, even more than legislative events do. We test our theory by analyzing discrete emotions in congressional e-newsletters and find that the affective content of these newsletters depends on whether members of Congress are part of the president’s party rather than whether they are in the majority or have legislative success. These findings reflect the emotions that rank-and-file co-partisans also feel toward the President and politics more broadly. Finally, using a survey experiment that keeps the newsletter’s informational content constant, we demonstrate that partisans evaluate lawmakers more positively when lawmakers express congruent negative emotions, such as anger and disgust, but mirroring positive emotions does not produce the same benefit.</p>