I'd thought Rush Limbaugh's spouting off on the "Obama's not black, he's Arab" idea was just an example of the so-called rat-effing that even the dimmest of New York Times reporters might pick up on. It seems to have spread more among the rightwingers than I'd expected, though.
I suppose it could just have accidentally resonated in minds driven by ignorance, fear, and anger. The other possibility is that it was focus-group tested, and its test result was the reason why Limbaugh gave it so much play. Always interesting to speculate about what goes on behind the scenes on the dark side.
The other interesting thing to think about is that this made-up nonsense hasn't worked now, so in four years people are going to be even less interested in lies about Obama's distant past. Republicans will be forced to deal with Obama's record instead.