Anchoring challenges through citizen participation in regional challenge-based innovation policies

•Discusses citizen participation in regional challenge-based innovation policies.•A process-tracing approach reveals how grand challenges anchor at the regional level.•Sensemaking, problem ownership, iteration and knowledge co-production are analysed as anchoring mechanisms.•Co-produced local, corrective and actionable knowledge shape the anchoring process. This study focuses on citizen participation as a co-productive and knowledge-intensive process in innovation policies concerned with regionally anchoring grand challenges. We apply a process-tracing approach and analyse citizen participation in two regional challenge-based innovation policies in the Ruhr, Germany. Local sensemaking, problem ownership, iterations and knowledge co-production are discussed as key mechanisms in the anchoring process. The results reveal the importance of a collective dimension in interpreting the local problem setting of a challenge achieved by reaching out to numerous citizens and how local, corrective and actionable knowledge facilitate the regional challenge anchoring. The policy formulation phase required the highest level of knowledge co-produced with citizens, followed by the implementation phase.