A variety of theoretical frameworks including social exchange theory, relational exchange theory, and contracting theory are used to investigate how to protect relational assets in a marketing channel when an upstream horizontal business combination between key suppliers arises. In this study, we ascertain downstream channel members' perceptions of a supplier's horizontal business combination both prior to and after such a combination.Our findings indicate that a normative contract breach resulting from a horizontal business combination influences downstream channel members by reducing their performance, decreasing their satisfaction, and increasing their likelihood of exiting the channel. Consequently, both the relational assets of the upstream supplier and their downstream customers are harmed. Importantly, these influences can be partially offset through the moderating effect of channel identification.