The current politicization of European integration was initially the result of the efforts of Eurosceptic political actors. However, under this growing pressure, even politicians in support of European integration, who previously exposed a tendency to avoid the issue, have expressed their positions more frequently. This paper investigates how the justifications pro-European politicians use to explain their positions affect public support for the European Union. I gathered data about the content of justifications for measures of European integration used by European legislators during the European constitutional convention, the Greek sovereign debt crisis, and the debate about open borders and migration. I then devised various laboratory experiments with diverse samples of participants as well as a survey experiment that is representative of the German voting age population. In the survey experiment, I randomly expose participants to one of the most popular justifications for the introduction of an integration policy, as established by the previous text analysis. Using data from the survey experiment, I test the expectation that Europhile politicians undermine support for integration by consistently using ineffective and low-quality policy justifications during different integration debates. The laboratory experiments allow me to elaborate on the psychological mechanisms of opinion formation about Europe that sustain people's responses to elite rhetoric.
