In the 2000 there were several states in which the black vote was 90% for Gore and that was enough, just, to make Florida important. If the black vote had wavered even a couple of percentage points in any of those Bush would have won the election comfortably.

Blacks are about 10% of the electorate. The ones that vote, vote about 90% Dem.

We’re going to see much higher than typical black turn-out this time and they’re almost all going to go Obama because “he’s black too” is why they’re voting this time. I’d guess that we’ll see 25-50% more.

So, the only black votes that McCain can pick up are among those who have been voting Dem. If he picks up 25% of them (which would be outstanding), he’ll move to 3% of the “currently voting”. That’s less than the number of first time black voters.

If Obama goes against teachers unions, they’ll swing more than 2% away from him. (Unions in general are probably most of dem support, and teachers are the biggest hitter, although probably not a majority by themselves.)

Obama’s already tacitly acknowledged the vulnerability of black voters on the education issue with his trial balloons about charters and performance pay at his NEA endorsement speech.

Now it’s up to McCain to force Obama to choose between the one group and the other.