Well, I just answered that in my post to you.
"Later, in the spring 2008, as Clinton’s chances of winning the Democratic primary grew thin, some of her hardcore supporters circulated rumors that Obama may not be a U.S. citizen, picking up on some of Martin’s innuendo and extending it further."
I mean, you can try and claim that in the context of the contemporary US Clinton fans constitute some sort of 'relative' left, but that doesn't work either, because in the context of that fight, of Hilary vs Obama, there is no sense in which they were slandering Obama because they thought he was too conservative, no way that they were doing that as representatives of 'leftism'. On the contrary, there has always been a strong streak of technocratic centrism around the Clintons, and in attacking Obama that way they were, insofar as it was anything more than purely personal ambition, acting for _the right_.
Now if you could show, say, Bernie Sanders using racism as a means of pushing an actual leftist agenda, then, maybe. But, while he might not have been particularly up-to-speed or aware of racial issues, I don't see any sign of his coming out with anything akin to 'superpredators'.
