Background: It is widely recognised that policymakers use research deemed relevant, yet little is understood about ways to enhance perceived relevance of research evidence. Observing policymakers' access of research online provides a pragmatic way to investigate predictors of relevance. Aims and objectives: This study investigates a range of relevance indicators including committee assignments, public statements, issue prevalence, or the policymaker's name or district. Methods: In a series of four rapid-cycle randomised control trials (RCTs), the present work systematically explores science communication strategies by studying indicators of perceived relevance. State legislators, state staffers, and federal staffers were emailed fact sheets on issues of COVID (Trial 1, N = 3403), exploitation (Trial 2, N = 6846), police violence (Trial 3, N = 3488), and domestic violence (Trial 4, N = 3888). Findings: Across these trials, personalising the subject line to the legislator's name or district and targeting recipients based on committee assignment consistently improved engagement. Mentions of subject matter in public statements was inconsistently associated, and state-level prevalence of the issue was largely not associated with email engagement behaviour. Discussion and conclusions: Together, these results indicate a benefit of targeting legislators based on committee assignments and of personalising the subject line with legislator information. This work further operationalises practical indicators of personal relevance and demonstrates a novel method of how to test science communication strategies among policymakers. Building enduring capacity for testing science communication will improve tactics to cut through the noise during times of political crisis.