We present an empirical demonstration that people rely on linguistic valence as a direct cue to a speaker’s group membership. Members of the U.S. voting public judge positive words as more likely to be spoken by members of their political in-group, and negative words as more likely to be spoken by members of their political out-group (three studies with 655 participants). We further find that participants perceive pluralized forms of nouns as more extremely valenced than singular forms (one study with 280 participants). This allowed us to control for the semantic content of words while eliciting systematic differences in the source attributions made by partisans. Our work contributes to both theory and methodology used to understand the linguistic cues people use to make social relational judgments.