• Studies about policymakers’ use of research evidence frequently track ‘evidence’ as opposed to tracking ‘use’. • Policymakers use evidence to inform their thoughts and decisions but also to influence those of others.• Policymakers’ communication with and about evidence is a reliable proxy of how and for what purpose they use evidence.• Methods from the field of persuasive communication can yield a rich and nuanced account of policymakers’ evidence use.This is a protocol to code documents about the policymaking process using a theory-grounded content analysis methodology. It looked at policymaking within U.S. Congress and the type and content of documents and evidence that was cited in deliberations