Maybe his campaign should air a couple good ads in SC in Q4, with pictures of his civil rights activist sit-ins in the 1960s ? Maybe it attracts more blacks to his campaign.
That wouldn't work. Nothing would work, tbh. Clinton will crush the other Dems among Blacks.
I don't think it's impossible for Sanders to get a decent share of Blacks, Hispanics, Asians and Native-Americans.
But there need to be a few factors for this to happen: Sanders needs to continue to gain in the "white" states of IA and NH in the coming months, do well in the debates and then defeat Hillary in those 2 states.
At the same time, the Sanders people need to run a flawless campaign, targeted at minority voters in SC, FL and NV - with ads of him and his working class policies such as a good minimum wage and against big corporations and billionaires (while showing Hillary as a corporate enabler and an out-of-touch big-business type who's wealthy herself and therefore not like the average minority voter).
Maybe then he has a chance in the later primary states due to momentum ...