Like many party systems across Western Europe, the Dutch party system has been in flux since 2002 as a result of a series of related developments, including the decline of mainstream parties which coincided with the emergence of radical right-wing populist parties and the concurrent dimensional transformation of the political space. This article analyses how these challenges to mainstream parties fundamentally affected the structure of party competition. On the basis of content analysis of party programmes, we examine the changing configuration of the Dutch party space since 2002 and investigate the impact of these changes on coalition-formation patterns. We conclude that the Dutch party system has become increasingly unstable. It has gradually lost its core through electoral fragmentation and mainstream parties’ positional shifts. The disappearance of a core party that dominates the coalition-formation process initially transformed the direction of party competition from centripetal to centrifugal. However, since 2012 a theoretically novel configuration has emerged in which no party or coherent group of parties dominates competition.