INTRODUCTION

Although the literature on political extremism tends to be structured around monographical descriptions of national experiences, a number of interesting regularities do emerge. I will treat as established facts the following ones. First, successful extremist movements and politicians (as well, of course, as extremist governments) generally stress several issues that are only loosely connected. Second, these movements or politicians often – but by no means always – adopt extremist positions on most or all of these issues. Third, when polled, supporters of extremist movements or politicians typically express moderate views on many issues. Fourth, many supporters of moderate parties hold views or adopt positions that are extremist with regard to some issues. This is especially true in countries such as the United States or Britain, in which there is no successful extremist party, but it can also be observed in countries in which one such party exists and defends these views. Fifth, it is often the case that people who support an extremist movement sincerely do not feel responsible for most of the positions adopted by this movement. This extends to the retrospective sentiments of many people with regard to their or others' past support of extremist movements, governments or regimes. Sixth, assessments of extremism vary over time. This applies in particular to retrospective assessments.