Sanders just bordering the center? Boy you need to see your analysts!
Yes, Sanders is a center-left social democrat who favors an expanded welfare state and worker-friendly policies. He wants to achieve them by using the existing mechanisms of electoral change, but with an emphasis on popular mobilization. He is the best candidate running for president, despite these limitations.
Center left? If so, could you provide a link showing the demographic of people who are to Bernie's left?
Socialists, communists, anarchists, syndicalists, people like that. People who are open and honest about being
anti-capitalism (which is what the entire left/right divide is about, not gay marriage or stimulus packages). Colloquially, I suppose any political situation has its left and right wing, but the broadest and most comprehensive picture should take views into account even if they aren't represented in the discourse of a given society. Just because we don't talk about them on mainstream news doesn't mean they aren't worth talking about, or that nobody takes them seriously. The family tree can get
pretty tangled if you try and name all the branches, which is why I don't bother classifying too much beyond the basics:
Center-left is social democracy (Sanders, AOC, Corbyn)
Left is Marxism-Leninism and its variants (Cuba for example, the USSR, periods in Venezuela, China, Chile, i.e. communism)
Far left is anarchism a la Noam Chomsky (no such states exist because it doesn't work)
Within those, you have different ideas about how to organize production, planning versus some degree of markets, how to balance protecting the revolutionary society against inevitable counter-revolution, and so on, all of which is of course different depending on whether your nation has been the victim of imperialism or is itself a perpetrator of imperialism.