"Why are the EU and immigration such complicated questions for political parties to compete on? And what challenges do they present to parties' electoral strategies? By systematically comparing the political mainstream in four West European countries -Belgium, Britain, the Netherlands and Sweden - this study explores the changing nature of party competition on two highly salient issues in contemporary politics. Based on a new way of coding party manifestos, and a large set of interview data, the author argues that the ideological ambiguity presented by the two issues can crystalize pre-existing tensions within parties. Furthermore, this study argues that an inability to negotiate these tensions explains why some parties are more likely than others to emphasise their successful track record of delivery and competent handling of EU and immigration matters, than they are to offer the electorate a choice between different societal outcomes"