Democrats and Republicans have increasingly sorted into homogeneous physical and online spaces and increasingly avoid contact with each other. Yet interventions that attempt to reduce partisan animus often rely on cross-partisan contact, an arrangement that can be hard to achieve in a workshop setting and even harder to sustain outside it. In this study, we evaluate a typical cross-partisan intervention alongside a more novel one that entirely sidesteps the challenge of bringing out-partisans together. Both are online workshops, but only the latter aims to change behaviors within rather than across partisan groups, teaching participants to recognize their own tendency toward outgroup animus and develop skills to challenge in-group members who use polarizing language. Field experimental evidence suggests that the within-group skill-building intervention diminishes partisan animosity, while the intergroup one does not. Given the challenges of facilitating intergroup contact in the US, it is promising that Americans can become less polarized without leaving the comfort of their own party.