In recent years, an emphasis on scientific argumentation in classrooms has brought into focus collaborative consensus-building as an instructional strategy. In these situations, students with differing and competing arguments are asked to work with one another in order to establish a shared perspective. However, the literature suggests that consensus-building can be challenging for students because their interpretations of the argumentative task and context may not enable their productive engagement with counter-arguments and evidence. In this paper, our goal is to explore the ways in which interactions of students support or inhibit their consensus-building. To that end, we examine and describe three cases that represent different ways in which initially dissenting students try to work towards a consensus with their peers. Through these cases, we demonstrate that legitimization of disparate or incorrect ideas can enable students whose arguments rely on incorrect ideas to feel that their ideas were heard and valued by the rest of their group. As such, we suggest that this legitimization is important because it can help students "save face". This enables students to move away from the competitive and persuasive aspects of argumentation towards interactions that align more closely with sensemaking and consensus-building. (Contains 2 figures, 7 tables, and 6 notes.)