This chapter reviews certain research that has focused on the evolving relation of Populist Radical Right (PRR) and mainstream politics, and in particular the strategic response of mainstream parties to the rise of far-right parties on the fringe of the political spectrum. It shows that they represent a new stage in the mainstreaming of PRR discourse, with a change in the fundamental dynamic of what has been called the "normalisation of the right". In addition to studying the effect of PRR politics on the political mainstream, the wave of scholarship starting in the 2000s has also reversed the gaze, and considered the influence of mainstream radicalisation on Populist Radical Right Parties. While it is unlikely the traditional rivalries between liberal and conservative parties will be completely displaced by emerging paradigms, political events in 2016–2017 have led to a radical shake up of party competition. The chapter also presents an overview of the key concepts discussed in this book.