Damn sure it works. You’d be surprised (or maybe you wouldn’t) at the numbers of people who identify as black or non-white on internet forums who insist that they can’t be racist “because I have no power.” That’s like saying they can’t be evil in other matters because they have no power. It’s almost impossible to dissuade them from their lunatic beliefs. And they swallow anything the Dem Party ladles out.
That is sort of a side issue.
Obama stirs up a lot of this type of animosity and jealously between groups because he and Dems are convinced that it will work up more Americans to go out and vote against Rs than it will other Americans to go out and vote against Ds.
The conventional wisdom is that those who would only vote D never R vastly outnumber those who will vote only R but never D.