This is an excellent analysis on at least two fronts: framing the Sanders effort in the context of counter-hegemony, and also the treatment of the centrists and median voter theory. If you are interested to see, we have also tackled these themes:

Our six part series on effective counter-hegemonic practice (here is part 6): https://www.indarktimes.com/city-trenches-counter-hegemonic-practice/

Our article on radical centrism: https://www.indarktimes.com/goldilocks-liberal-centrist/