Obviously, one's opinion of what is extreme and moderate depends on where one stands. When making blanket comments (such as those made by me and you), it is futile to use external factors (ie. other countries) or your opinions as the standard by which to measure and judge the social norm. For this reason, I have used the US political spectrum as the standard. By this standard (which is the only relevant standard when discussing US politics), there are many far left adherents in the past and present who wield political power. Whether you consider them "far left" is irrelevant. What is relevant is whether they are outside of mainstream American political discourse. That is what will determine whether they are far left or not.
I'm a bit disappointed that you accuse me of being indoctrinated. I have strong views that cross the political aisle, and some would call me a liberal. Regardless of political belief, labeling those who hold opinions with which you may not agree as being indoctrinated (or stupid) is immature at best and fanatical at worst. While I anticipated your entry into this discussion (and looked forward to an exchange of ideas), I expected a higher level of discourse.
Just to be devil's advocate, I'll play your game. On a worldwide political scale (which as I pointed out earlier is meaningless to this discussion), one can safely say that countries such as Cuba, Venezuela, India, and Brazil lean left to varying degrees. There are many US politicians who openly espouse fundamental elements of the socio-economic-political systems by which these countries are managed. I'd rather not point out specific examples since that would take us even further off-topic (if that's possible), but it is very obvious to even a casual observer. This, by itself, disproves your assumption that "moderate center left" adherents have never had political power in the US.
Apologies to Inprov for the tangent.