Political parties are ubiquitous features of contemporary models of representative democracy and are widely believed to be integral to transition, and yet persistently democratic Pacific Island countries tend to have ‘weakly’ institutionalised parties – some have none at all – that have little influence on the mobilisation of voters during elections. Party theory largely assumes that politicians form parties to win elections: the author asks why, given the commonly cited irrelevance of party politics in much of the Pacific, politicians join political parties at all. Drawing on 96 biographical accounts – including 72 in-depth interviews –he interprets the explanations politicians give for joining, leaving and changing parties. The author identifies three narratives. The first accords with an augmented rational actor model, the second with a responsible parties model and the third points to intrinsic motivations that are largely overlooked in the existing literature. The author concludes that a comprehensive account must include all three interpretations.