A Party with it's power based on rural black population would be doomed to failure. Besides African Americans only making up 15% of the nation, not to mention that a good number of black people ARE NOT in the ghetto, nobody would ever take you seriously above the small scale with a power base from inner cities. And any sort of support for Black Nationalism would be the death of the party. I'd broaden the scope at the very least, and include any sort of impoverished minorities as well as trying to drum up support from poorer white people.
But I don't think you really understand the divide in the ghetto at all. Its a lot more complex than just poor African Americans in the inner city somewhere, and between racial conflict and "white flight" having your power base in the ghetto would be damning.
African Americans only make up 15% of the population but they also make up 82% of the population of Detroit, the overwhelming majority. Don't kid yourself - the majority of people in the ghetto are black. That's just the sad fact. In the UK, we've got quite multicultual impoverished areas, although they often have a white majority. The areas in the USA I'm thinking of would be former Socialist (Black Panther Party) power bases.
There is racism, then there is nationalism. They are often combined but are not inseperable. Black nationalism, if championed in a way that did not make it anti-white, is not racism, just promotion of black identity, culture, language, music etc. I think in order to really make an impact in black areas that are as bad as Detroit, you would need to do something quite radical - you're going to be clashing with a culture that's been developing for decades and is really quite deeply set. Harkening back to the old days may be the only way to break through that.
I also make this prediction - black people in the USA will eventually feel marginalised in politics after the focus in minority politics shifts heavily towards Hispanic people, as it should do, seeing as they will form a growing majority in many states. Maybe socialism, if led by the right kind of figureheads, would be perfect for their group.
Secondly, African Americans as a demography are economically liberal, but socially conservative. I wouldn't expect an acceptance of blatant socialism, given how even liberal Americans react to the word, regardless of the concept.
I don't think that's very significant. Many of the countries that were openly Socialist in the 20th century, or at least had strong Socialist factions, were very socially conservative. Russians, Chinese, North Koreans, Scots, Welsh, Northern English, Poles, the list goes on.
Of course - this isn't to say that, as MetalSlimeHunt says, one couldn't target both New England and black majority areas. That said, it would be difficult to unify the two factions. Perhaps the answer isn't go for black nationalism outright but try to harken back to the Marxist ethos of the old black nationalist groups that were once very powerful in black communities. Maybe a sense of continuity was all I was thinking of. I'm sure talented propaganda artists could succeed with that.