The League is rapidly losing support and its leader, Matteo Salvini, may take drastic action.
Italy's deputy prime minister remains immune from prosecution because his coalition partners, the Five Star Movement, let members vote online to uphold it.
The new coalition's spending plans will ramp up Italy's annual budget by over €100 billion a year.
While often lumped with other European populist parties, Beppe Grillo's M5S is a movement of activist fans mobilized by the messages of his "celebrity brand".
Italy's political future hangs in the balance – will it see another chaotic grand coalition, or take an anti-EU populist step into the unknown?