This conclusion presents some closing thoughts of the key concepts discussed in the preceding chapters of this book. The book explains why radical right-wing populist parties moved from the margins into the mainstream and, it explains mainstreaming' provided by the inclusion-moderation thesis, which holds that participation in democratic institutions and procedures will amend the radical nature and ideology of political parties. The inclusion-moderation focuses on electoral competition and office participation, an argument that has been elaborated and qualified in the theoretical framework. All Western European radical right-wing populist parties that have been selected for the case-studies in the book DF, FN, FP, FrP, PS, PVV, SVP, VB and UKIP are parties that fully participate in democratic elections. Most parties, apart from VB, FN and UKIP, also have had opportunities to enter national office. Various parties are still young with a relative short socialisation in democratic electoral competitions, representation or office.