Niche parties have established themselves in Western European party systems by focusing mainly on culture. Yet, with growing professionalization, these parties start to diversify their issue portfolio. A social policy agenda connected to their core issue – such as a welfare chauvinist programme for the Radical Right and an egalitarian agenda for the Greens – might help to attract new constituents, and to break with their single-issue image without losing credibility on their core issue. However, while some of these parties have been active in promoting a social policy agenda, others have remained almost silent on issues outside their niche. This article investigates how parties’ internal preference distribution affects their divergent issue engagement. It draws on different measurements of intra-party preference heterogeneity using both survey data and parliamentary speeches in combination with Latent Semantic Scaling. The analysis finds that, in contrast to mainstream parties, niche parties engage in social policy issues once they are characterized by higher levels of preference heterogeneity. By showing that niche and mainstream parties deal differently with internal preference heterogeneity, this paper contributes to the understanding of broad appeal strategies, and indicates that niche parties use their blurred position to strategically appeal to new voters.