The limits of tailored online campaigning

• Department of Political and Social Sciences

This session of the Political Behaviour Colloquium features a presentation by Frederik Thieme, a PhD Candidate at Humboldt University of Berlin

How effective is tailored online political advertising in mobilizing voters? We argue that appeals resonating with salient voter identities, such as gender and parenthood, should increase engagement and turnout. To test this, we conducted a large-scale field experiment with the German Green Party during the 2024 European Parliament election, randomly assigning ZIP codes to receive either generic or identity-tailored ads targeting middle-aged women. The campaign reached over 686,000 women. Using official election returns and a post-election survey, we find no evidence that tailored ads increased turnout or vote share, with survey data revealing low platform penetration and ad recall among the target group. To distinguish between a failure of message content and a failure of delivery, we complement the field experiment with a survey experiment among German women (N=5,394). The survey experiment finds positive effects of tailored messages on propensity to vote for the Greens, particularly for care infrastructure appeals among mothers, with effects attenuating among less attentive respondents. Taken together, the evidence suggests that the null field result reflects a failure of delivery rather than of content: tailored messages can persuade when they reach their audience, but platform constraints and scarce user attention severely limit meaningful exposure in practice.

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