In March 2015, Bandić founded a new social democratic political party, the Bandić Milan 365 - Labour and Solidarity Party (BM 365). Bandić commented that he was always a social democrat and described Zagreb as the most socially sensitive European capital. In the same month, Bandić's supporters organized a petition called "Stop political arrests". Among the signatories were Croatian film producer Branko Lustig and former Finance Minister Slavko Linić. The BM 365 won seats in the 2015 and 2016 parliamentary elections. The party won a majority in the Zagreb Assembly in the 2017 local elections, and Bandić was re-elected mayor for a sixth term. A coalition was formed in the Assembly with the HDZ.