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When Politicians Misread the Public: Experimental Evidence that Politicians Underestimate Climate Policy Support and Norm-Based Solutions https://doi.org/10.17863/CAM.124777 Tanase, Lisa-Maria 0000000230726668 De-Wit, Lee Because of the systemic influence of politicians’ decisions, and the striking disconnect between public demand for climate action and governments’ limited responses, this thesis investigates: Do politicians underestimate public support for climate policies? The social norm literature shows that citizens often underestimate climate policy support, contributing to a Spiral of Silence that discourages advocacy. Whether politicians hold such misperceptions remains an open empirical question, with serious implications for democratic representation, trust, and the pace of climate mitigation. The Introduction reviews the literature on social norm misperceptions and outlines the rationale of this thesis. This PhD was designed as a “full circle”: first integrating politicians’ perspectives to inform subsequent studies, then experimentally testing and correcting underestimation of climate policy support in current politicians, and finally returning the findings to those policy actors best placed to act on them. Chapter 1 presents qualitative results from interviews with former UK MPs, exploring whether perceived low public support is viewed as a barrier to political climate action. Chapter 2 presents an experiment with 611 Belgian politicians from Flanders, testing underestimation of climate policy support, and whether this underestimation can be reduced by a norm-based intervention presenting polling data evidence, polling data combined with dynamic norm evidence, or evidence of existing perceptual biases within politicians. Chapter 3 examines whether in a study with 617 participants from the UK public, such underestimation exists among citizens, and compares two norm-based interventions: Polling data vs. polling data accompanied by information on how public support changes when policy costs are made salient. In Chapter 4, an experiment with 100 UK Members of Parliament tests whether they underestimate climate policy support in the public, in voters of key parties in the UK, and in other Members of Parliament, and whether polling evidence reduces underestimation post-intervention. This thesis: (1) Presents some of the first evidence of politicians’ underestimation of climate policy support, both in UK and Belgian politicians. Notably, the study finds that UK MPs also underestimate the proportion of the public who report supporting climate policies when the personal costs of those policies have been explicitly presented to the public. (2) Introduces novel evidence that politicians overestimate political polarisation in the public. They also form significantly larger underestimation when they estimate climate policy support in right-wing party voters. (3) Provides some of the first experimental evidence of the Spiral of Silence within Members of Parliament, finding they are less willing to speak up in support of certain policies when they perceive the policy’s public support to be low. (4) Finds significantly larger underestimation of public support in politicians opposed to a climate policy, and evidence that even supportive politicians underestimate on average. (5) Offers one of the first interventions aimed at reducing underestimation of policy public support within elected politicians. Chapter 5 presents the policy engagement this research has generated, including a policy workshop I organised at the Royal Society, with senior guests from the UK Parliament, House of Lords, and across government, for which I was awarded the Policy Innovation Grant by the Centre for Science and Policy. The P.E.R.C.E.I.V.E. framework I developed to engage policymakers with my findings has been used by key policy stakeholders in UK and Danish Governments, the EU Commission, and contributed to the evidence inquiry of the Parliament’s Net Zero Select Committee. University of Cambridge 2025-09-09 Thesis Doctoral Doctor of Philosophy (PhD) eng El-Erian Scholarship Centre for Science and Policy Innovation Grant Award https://www.repository.cam.ac.uk/handle/1810/395195 https://www.repository.cam.ac.uk/bitstreams/726fb993-70f5-4648-ad63-937b266a2f17/download 0b889757ce605c450350a5dcad209abe https://www.repository.cam.ac.uk/bitstreams/fde1712a-6232-4234-879a-e164d4d1e830/download 87eda9de84448d1f82354d60eee3eb5f https://creativecommons.org/licenses/by-nc/4.0/ politics psychology