In the United States, several hundred interest groups and other political organizations provide annual ratings of members of the U.S. Senate and the U.S. House. These ratings are meant to reflect members' support for the legislative agendas of the groups in question. With focus on the U.S. Senate, this study considers the possibility that a psychological factor--variation in the core personality traits of senators--also influences how favorably or unfavorably senators are rated. The detection of personality effects would add to the growing body of evidence regarding the tangible significance of elite personality, while also providing suggestive evidence that interest group ratings may not be entirely pristine representations of legislators' stances on the policies of relevance to the rating organizations.