There is nothing scientific about a poll here. Do you have any data besides that?
But you acknowledge that the racist component is indeed there.
The flaw here can be illustrated by an example. Let's suppose a man wants to go and spend one thousand dollars on a gun, but his wife does not approve and is very vocal about it. Instead of buying it right away, he waits for a year or two, buys it and stores it in secret. The wife has put up an obstruction, but she has not stopped him from buying the gun. The point is this, an effect does not NECESSARILY mean that someone is unable to do something. Rather the effect could be an obstruction.
That said, to prove that it has had an effect consider this. It is a fact that SOME on the right, appeal to the racist sentiments in whites to get votes. SOME on the left do it as well, but there is no doubt that SOME on the right do it. They do it because it is effective. On of the mechanisms that presidents refer to when the are trying to form a consensus to advance their agenda is the mandate that they have from the electorate. They base that mandate on the margin of their victory. It is a fact that there are some on the right, and on the left that voted against Obama because of his race. THAT IS FACT. As such, the mandate is eroded, thus putting up an obstacle for Obama in the advancement of his agenda. There's the proof.