Global warming is not only a serious threat for humanity but increasingly structures political competition in Western Europe. The rise of green (niche) parties and public awareness of the issue pressure mainstream parties to emphasise climate protection. Yet, while scholars reflect on the factors influencing mainstream parties’ environmental agendas, we know little about what triggers climate standpoints and about the role public opinion plays in this process. This study measures the salience of climate protection in 292 election manifestos of mainstream parties in 10 Western European countries since the 1990s and estimates the impact of different factors on their climate agenda using OLS regressions. The findings suggest that green parties are not the driving factor, and that it is the public salience of environmental issues and pressure from the Fridays for Future movement influencing mainstream parties’ agendas. Accordingly, mainstream parties seem to be responsive to public opinion pressure adopting climate protection stances. The study further proposes a different measure of niche party success than that used in previous studies.