We develop a theoretical and empirical approach that captures the degree of issue politi- cization through three components: salience, conflict, and diffusion. As politicization is a communicational process among politicians, we rely on elite communication on social media. This choice allows us to address important limitations in the literature and study all three facets simultaneously. Using a combination of human coding and machine learning we examine if and how MEP candidates politicized the EU in the 2014 European Parliament elections. We show that when mainstream party candidates face constraints related to their control of salience and conflict around the EU dimension, they will resort to disengaging the public in order maximize their electoral gains. This contributes to lower levels of politicization compared to national issues and offers a communicational mechanism for the success or failure of issue entrepreneurship. In sum, by taking the multifaceted nature of issue politicization into account, we are able provide new insights on why and how issues become politicized.
