The fact is that blacks vote in a block. The last presidential election showed that when 90% of the black vote went to Kerry. I think that getting them to switch is something you might be able to do for a second term, but they are too firmly entrenched in their voting habits to change it with 11 months remaining, better to concetrate on those who've bever voted or who have dropped out of the process.
And since white males are the single largest voting block, why would you be so dismissive of them in order to pander to a group that is unlikely to switch party affiliation?