The Italian Communist Party is often faulted as a useless Eurocommunist experiment, but during the second half of the 20th century, the possibility of communist rule in Italy was very real. The party came very close to power in the 1970s, becoming the second-largest party with a peak of 34% of the vote in 1976. I want to know what would have happened if they had won? Could the collapse of 20th-century Socialism have been delayed or averted completely? Or would the PCI have just governed as Social Democrats, ceding power once they were defeated?
If the PCI outright won general elections, and managed to form a government, most likely you would have had a version of what happened in Chile in 1973. The Americans would absolutely not allow a 'communist' government to rule and would undermine it at every step of the way. The Italian establishment and armed forces would take steps to ensure the government's quick downfall.
They already had lots of plans to "fight Communism" (Operation Gladio, the P2 Lodge, Golpe Borghese etc. Etc.)
Their successor party, the PD did win. What makes you think that they would've been different under a different name?
The aldo moro case is an interesting conspiracy , was it agent provocateurs