Yes, I think that's true. Carter and Bush I both had approval ratings that sank into the 20s at some point during their tenure. Yes, they did rebound, but they never fully recovered. Obama has, I don't believe, ever sank beneath 43% in most polls. That's problematic.
I also think that so long as he enjoys minority support above 90%, it may be (as a practical matter), virtually impossible for him to dip below 40%. That too is a problem.
Why what are you insinuating?
That possibly people will vote for someone on the basis of his race? Why that would be ra...!