The study of sustainability transitions (SUSTRANs) is an emerging research field that provides useful keys to understand how more sustainable ways to meet societal needs may emerge and develop. As stressed by some scholars, much more work is needed to make political institutions endogenous to SUSTRANs. This paper contributes to such a research endeavour by providing a simple conceptual framework based on multiple levels of Darwinian evolution. The evolutionary environment is defined by a societal function (e.g., urban mobility), which is fulfilled by socio-technical systems (STSs) (e.g., the car, public transport, the bicycle, etc.). Three levels of evolution are considered: a lower level, with firms; two higher levels, with innovation networks and socio-political communities, respectively. While competing within the same STS, firms cooperate within a socio-political community in order to back their STS, and compete with other – both existing and emerging – STSs that fulfil the same societal function. With this simple framework SUSTRANs can be represented as a multilevel evolutionary process that endogenously generate the needed favourable policies (FPs). A socio-political community supporting a new and more sustainable STS achieves the ability to induce FPs only if it is able to scale up – and reach a tipping point – in the cumulative causation process between the enlistment of new members and an increasing level of legitimation. The proposed framework can be applied not only to SUSTRANs, but to all socio-technical transitions, where power and competition can be considered as multilevel phenomena, and multi-industry dynamics are at centre stage.