"Elections in advanced democracies have become increasingly unpredictable in recent years. New political elites and former pariah parties are gaining popularity while traditional, mainstream parties and leaders lose support. Perhaps most notably, Europe is in the midst of its most tumultuous electoral era since the inter-war years. Unconventional parties with leftist, rightist, and ideologically ambiguous platforms attract voters in political contests across the continent. Vote shares of Europe's establishment parties such as left-leaning Social Democrats and right-leaning Christian Democrats are in precipitous decline in many countries. Election campaigns are increasingly confrontational, suggesting that the post-war commitment to political consensus among political parties has weakened. As challenger parties grow in popularity, they stand to further transform the nature of political competition and policy making. They also stand to alter political systems for decades to come as young generations enter a very different political environment than the one that ushered their elders into democratic citizenship"--