 They were marked by a victory of the Communist Party (PCI) passing from 25% of 1963 to c. 30% at the Senate, where it presented jointly with the new Italian Socialist Party of Proletarian Unity (PSIUP), which included members of Socialist Party (PSI) which disagreed the latter's alliance with DC.PSIUP gained c. 4.5% at the Chamber.The Socialist Party and the Democratic Socialist Party (PSDI) presented together as the Unified PSI–PSDI, but gained c. 15%, far less than the sum of what the two parties had obtained separately in 1963.