I specifically examine why some extremist organizations quickly decided to participate to elections while others resisted a party strategy. In addressing this question, I pay particular attention to how institutions (most notably electoral rules) and the competition between these extremist movements and conservative political parties provided incentives and disincentives for these formations to seek representation in legislative assemblies. I also address how the socio-economic characteristics of the members of these movements affected the strategy of party formation. Based on internal documents from several European extreme right formations, and using qualitative and quantitative methods, I show that, more than the institutions or the competition with other parties, the sociological composition of these movements affected their incentive structures and in large part explained their response to electoral politics.