This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book addresses the significance of mainstream party positioning in affecting the success of the populist radical right (PRR). More specifically, it seeks to challenge those conclusions which suggest that the PRR option is the only alternative for voters whose preferences fall in the reductionist and/or assimilationist spheres. The book considers Meguid's framework for depicting mainstream party responses to niche challengers. Meguid argued that one of three strategies can be used to counter the electoral success of the PRR, namely accommodative, dismissive, or adversarial approaches. With reference to the Danish case, the book highlights particular 'institutional arrangements' that affected those inter-party negotiations taking place before and after an election. In order to avoid a political stalemate, Danish governments have often been willing to grant concessions on issues prioritised by their support partner/s, even if these concessions sometimes go against what the government actually wants.