Obama's job rating among black voters is 91% positive. A lttle back of the envelope arithmetic suggests that Obama's job rating among the 88% or 89% of non-black respondents is about 39% positive and 54% negative.

That's pretty weak - a whole lot more negative than the numbers you usually see for all voters. This is hugely relevant to the 2010 elections. Most of the states with seriously contested Senate races or Democratic seats that seem almost certain to go Republican have below-national-average black percentages. Exceptions: Arkansas (where polls show Democrat Blanche Lincoln well behind), Florida, and Illinois.

Similarly, when you look at the list of target House seats very few have substantial black populations. This is partly the result of the prevailing interpretation of the Voting Rights Act - supported and encouraging by most black Democratic politicians -which requires maximization of the number of "majority-minority" districts. When you put lots of black voters in those districts, you don't have many in adjacent districts.

All of which is to say that the state of opinion in the real political battlegrounds of 2010 is considerably more negative toward Barack Obama than top-line poll numbers suggest.