The global phase-out of coal by mid-century is considered crucial to achieving the Paris Agreement and keeping warming well-below 2°C above pre-industrial levels. Since the Powering Past Coal Alliance’s (PPCA) inception at COP23, political ambitions to accelerate coal’s decline have mounted to become the foremost priority at COP26. However, mitigation research lacks the tools to assess whether this bottom-up momentum can self-propagate toward Paris-alignment. Here, we introduce Dynamic Policy Evaluation (DPE), the first evidence-based approach for emulating real-world policymaking. Given empirical relationships established between energy-economic developments and PPCA membership, we endogenise national policy decision-making into the integrated assessment model REMIND via iterative, multi-stage feedback loops with a political feasibility model. DPE finds the PPCA ~5% likely to diffuse globally – indicative of baseline coal exit ambition – and exposes severe, unconventional risks of current power-sector-specific action. Furthermore, PPCA evolution exhibits path-dependence to Covid-19 recovery investments, illustrating DPE’s utility for exploring policy synergies.