This project focuses on the interrelations between the micro-level of popular attitudes to European integration and the macro-level of elite justifications for pursuing membership. Drawing on extant research on Eastern Enlargement this study develops an approach of ‘theoretical differentiation’ and distinguishes between rationally oriented ‘Utility Maximizing’ entrants (UM) and constructively driven ‘Value Maximizing’ countries (VM). ‘Theoretical differentiation’ in elite attitudes then, becomes the default drive in empirically investigating public support for the EU. First, explaining the dynamics of utilitarian public attitudes, this study ‘differentiates’ the short- term, economic factors from the long-term, elite-driven stimuli that render the UM group of countries more eurosceptic than the VM group. The regression analysis shows that while in both groups short-term support fluctuates with the business cycle, the intensity of long-run support is determined by the set of structural characteristics that identify them as either UM or VM. Similarly, ‘differentiation’ in affective support shows that the latter is a mixture of the longterm disposition towards EU, determined by historical elite attitudes, and the current socialization factors that govern short-run variations. Yet, the affective attitudes of the two groups not only differ in their mean levels of support (i.e. intensity) but also in their responses to direct and indirect socialization stimuli (i.e. fluctuations). In other words, EU enlargement politics and the distinct elite frames they produce increase the stickiness of affective attitudes to European integration and partially regulate the utilitarian public sentiment. Both utilitarian and affective models of EU public opinion were tested at the aggregate level of survey respondents, using Eurobarometer polls from the fifteen ‘old’ member states. OECD data were compliled to control for the economic factors, while original data on the national distribution of EU officials in the Commission and the European Parliament were gathered by the author to control for the EU socialization stimuli.