A steady decline in major party support in Commonwealth nations has resulted in changing parliamentary compositions, including the growing prevalence of minority government. Such situations pose new questions for notions of government legitimacy within Westminster systems. For instance, is negotiation with cross-benchers an example of government illegitimacy? What is the legitimate role of non-ministerial members when the composition of parliament gives them the final say on the enabling legislation for public policy? What is the legitimate response of the public sector regarding policy-making in the context of minority government? In this paper, we reflect on how a 'marginal member' concept can provide new insights into such issues and their implications.