This study examines the impact of mainstream political parties’ strategies on the Australian Greens, a ‘niche party’ associated with the global warming issue. The Green vote rose between the 2004 and 2016 elections despite voters’ support for action on global warming declining. Meguid (. Party Competition Bbetween Unequals: Strategies and Electoral Fortunes in Western Europe. New York: Cambridge University Press) proposed that mainstream parties must decide whether to dismiss, accommodate, or oppose a new issue and niche party, predicting the impacts using the theory of ‘issues-based voting’. We use a time series of voting intention to test this theory. Mainstream party strategies had the predicted effects on the Greens vote. In the presence of a competitive niche party, mainstream parties’ strategies may respond to the dynamics of competition, beyond the traditionally considered institutional and economic forces.