For all the day-to-day changes, the parties have actually been surprisingly faithful to their overarching ideologies. However, in no way has this stability precluded change. The main claim made in this article is that, on the contrary, in several instances it appears that the only way of keeping up ideological stability is through policy change. The kind of stability based on an ongoing adaptation and change might be the very triggering cause behind the successful opening up of a policy window. By offering a firm point of reference, ideology analysis could function as a bridge between ‘formative’ approaches – which indicate some degree of actor freedom — and ‘path dependency’ approaches – which stress deterministic structuring by institutions – and provide one of the missing links between institutional and rational choice analyses.