Blacks who choose to go to the polls this time around will continue to vote for Obama...however, if the numbers continue to be tight, then what could hurt him is the lack of enthusiasm by all of his former supporters. People who were invested in seeing a black man elected already achieved that goal, so now some of them will be fine to go back to sitting on the couch and bitching about all the politicians.
Like I said in another thread, you don't know the black community. Obama will garner more black support than in 2008. Even the blacks that oppose gay marriage, in the article, say they will support Obama. Do you know why? Because the black community sees the attacks against Obama from the Republicans as mostly based on his race. It now is an "us vs them" issue and Obama is "us". You have alot to learn about the black community.