Buffy I'm not sure if the mainstream media does so much, at least while he's in power, but the religious right, the GOP and others certainly allude to it. No one will come right out and say it in print media, but a lot of people I've argued spoken to have definitely got it in their heads that he's messing up because he's black, and that his missteps will come back to haunt any future black presidential candidates.
I suspect that, should there be another black presidential candidate in the near future, there will be a fair amount of people on the opposing 'team' suggesting that because Obama has done x, then any black president could potentially do it too.
Sorry, a bit rambling, but the upshot is, yes, I believe that, certainly with the GOP faithful, so old, white and rich, that any misstep by Obama will be seen as reflecting on any black person in a position of relative power.