Rasmussen polling may be off like every other poll, however what is good about Rasmussen is they stick to good standards on sampling pool so at least trends can be derived from their work.

As you can see Trump is polling at 40% with Blacks. No Republican has done that since Calvin Coolidge in 1924. The second thing is Trump is now at 50%, 6% points higher than BHO at this point in his presidency. Other take aways, The general electorate is split evenly on Trump, either you love him 80% or hate him 80%, while he holds a +6% among independants and Whites. Men and women are split 50-50.
We'll see how well Trumps increased popularity transfers to mid-term candidates, but he is definitely working hard. He has 11 Rallies in 8 states over the next 6 days.