Our substantial interest is to account for the impact of campaign effects in the context of a popular vote on a strengthening of national climate change policy. Nation states need to increase their ambition to achieve the 1.5° goal stipulated within the Paris Agreement. In this paper, we estimate how the tone and topics of the media can sway people with different demographic characteristics and self-interests during a campaign on a vote on climate policy. We want to know whether campaigns inform voters about their own positions on a given issue, and whether self-interest trumps elite cues provided by parties and associations. To this end, we conducted a two-wave panel survey experiment in Switzerland during the campaign leading to the popular vote on the CO2 law on the 13th of June 2021. Switzerland is an ideal setting for this study as we can measure the change in peoples’ opinion on climate change separated from other issues. We collected data from news articles and twitter to estimate the sentiment and the topics of the media coverage during the campaign. Preliminary results show that campaigning on cost and cuts in mobility by the “No” campaign had a larger impact on younger people, despite their overall higher support.