Yeah but what was the basis of Clinton's non-black primary support in 08? She won working class voters because a lot of them saw Obama as a Lincoln-praising neo-liberal from blood red Kansas.
Uh, wtf?
The idea that Sanders is raking in white working class votes is unsubstantiated. This is a generational struggle, and nothing else. The advantage Sanders has with low-income whites is almost entirely a product of the age gap, i.e. younger voters tend to have lower incomes and also tend to support Sanders. See also: the "marriage gap" where single voters were more likely to support Sanders.
We saw a similar age gap in 2008, with young voters supporting Obama, and this was coupled with similar income and marriage splits. The difference is that Sanders, unlike Obama, doesn't have African Americans to bolster his numbers.