Abstract: An influential perspective argues that voters use interest group ratings and endorsements to infer their representatives' actions and to hold them accountable. This paper interrogates a key assumption in this literature: that voters correctly interpret these cues, especially cues from groups with whom they disagree. For example, a pro-redistribution voter should support her representative less when she learns that Americans for Prosperity, an economically conservative group, gave her representative a 100 per cent rating. Across three studies using real interest groups and participants' actual representatives, we find limited support for this assumption. When an interest group is misaligned with voters' views and positively rates or endorses their representative, voters often: (1) mistakenly infer that the group shares their views, (2) mistakenly infer that their representative shares their views, and (3) mistakenly approve of their representative more. We call this tendency heuristic projection.