Globally circulating models have come to exert a pervasive influence on social policymaking processes.  Sometimes styled as best practices, occasionally sold as silver-bullet solutions, global policy models serve as carriers of policymaking rationalities.  As objects of inspiration/emulation, they shape the terms and the terrain of reform debates, mobilizing a form of preemptive, technocratic power.  They preconstitute both fields of action and modes of intervention, in the process reproducing as well as realizing dominant paradigms, while effectively foreclosing the deliberative consideration of alternatives.  Having succeeded elsewhere, they travel not only with the pragmatic promise of “workability,” but typically also with the imprimatur of multilateral agencies, expert networks, and evaluation science.  For all their power and influence, however, global policy models are not simply remaking the world in their own, immaculate image.  The immodest discursive reach of these models routinely exceeds their prosaic grasp, as the source of replicable results.  They are not rolled out quasi-automatically, across fields of seamless transfer, but in practice are associated with serial underperformance and tangled webs of contradictory mutation.  As a result, there is always a politics to policy mobility, and there is never a shortage of surprises in the netherworlds of practice and implementation.