The Hungarian Fidesz party is confronting an existential crisis after its historic defeat in April, when Péter Magyar's Tisza party ended Viktor Orban's 16-year rule and stripped Fidesz of its parliamentary supermajority. The party, which played a major role in Hungary's democratic transition in the late 1980s before becoming the vehicle for Orban's nationalist and eurosceptic transformation after 2010, is now struggling to determine how it can survive in a radically changed political environment.

Insiders say Viktor Orbán's party is looking into the abyss amid corruption scrutiny, a wave of senior departures and Tisza's dominant poll lead. Orbán's personal future in…

The Hungarian Fidesz party is confronting an existential crisis after its historic defeat in April, when Péter Magyar's Tisza party ended Viktor Orban's 16-year rule and stripped…