The effect the blacks have on the polling is quite large when they overwhelmingly support Obama. You have to figure blacks are very much trending up Obama's support among democrats, unmarrieds, men, women and the regions where they are found in most abundance. Obama's support amongst whites is quite low, indicating even a lot of white democrats aren't happy with him.
What is interesting is that despite Obama being viciously pro-amnesty, almost 50% of hispanics don't favor him. At the least this indicates a sizeable amount don't mindlessly support democrats. One has to wonder why blacks overwhemingly support democrats. Has he done anything of real note to support the black community? One could make a case that Bill Clinton reached out to blacks a fair bit in his tenure as president, as they called him the first black president. What has Obama done, other than being a black man himself? Are the blacks in America following their brothers and sisters in places like South Africa and simply supporting a black leader because they are black? Inquiring minds want to know.
As you pointed out, how is it possible that 23% of conservatives support him? Who are these people who call themselves conservatives and support his policies? I suppose they could be the anti-war, anti-semite, paleo-con types like Pat Buchanan? I can assume the 12% of republicans who support him are probably the liberal republicans like Mike the Kike Bloomberg.