If Nader isn't a raving socialist, then your bar is so high Marx couldn't have leaped it.
Ever read the Green Party platform?
What's funny is that as the mainstream Democrats move further and further leftwards, the criteria for what makes a real socialist or communist has to be shoved ahead of them, until after a while the definitions become meaningless. To hear some leftists talk, there never was any such thing as communists in the United States.