The words communism and socialism are not meant to be defined, their purpose is to put fear into the American people. The Republicans have been using these fear words since the Thirties when the battle over Social Security began. Since that time they have been used very effectively, by naming every Democratic president as a socialist and/or communist, and most of their programs socialist, bordering on communism.
The antidote is research, what do those words mean, and what is their application to America. Will Social Security really turn America into a communist nation? Was Truman really a socialist? Truman, the man, that when a corporation offered him a post-presidency job at a great salary, said, You don't want me. You want the office of the president and that doesn't belong to me. It belongs to the American people and it's not for sale."
One puzzle, why haven't the words fascist and Nazi ever gained the popularity or use as the other two words? As scare words they are pretty much a fizzle.