Founded just five years ago, the Alternative for Germany (AfD) represents the biggest opposition party in the German parliament. This article addresses three questions in European comparative perspective: What is the nature of the AfD as a relevant political party in the Bundestag? What explains its rise and popularity? What is the party's behavior and impact in parliament, and on German politics in general? Examining platforms, the article first identifies programmatic and ideological shifts that have turned the AfD from a single issue anti-Euro party into the first radical right-wing (populist) party in parliament since the Nazi era. Second, voter analyses suggest that the AfD's political radicalization has not undermined but increased its appeal. Third, the robust electoral support for radical positions makes it likely that the party seeks to further deepen political conflicts. Behavior in parliament shows that the party follows its European counterparts' polarizing strategic orientations, reinforcing the Europeanization of a nativist sociocultural "counter-revolution."