Could the disparate group of campaigners and anti-establishment politicians be a real electoral threat?
Matteo Renzi's center-left government could face tough contests in four cities.
The legislation has reached a deadlock over a provision for adoption.
Former PM cleared of paying for sex with minor after being sentenced to seven years imprisonment in 2013.
Berlusconi's petition to have the sentence reduced was filed last month and approved on Monday.
Renzi's Democratic Party and a handful of allies pledged on Thursday to back constitutional court judge Sergio Mattarella.
Leader of Italy's surging right-wing Northern League says "Russia represents the future"