I can remember 50 years ago as a kid listening to some of my Italian aunts gossiping about others and referring to one individual or another as "that one" instead of by name. I later learned it was a way to show disrespect without using coarser language. It was not uncommon during the 1950s and before, but wasn't needed because so many other terms of disrespect became common and socially tolerable from the 1960s to today. So while the phrase is not specifically racist in that it can be applied to anyone, it demonstrates two things. First, McCain dislikes Obama so much, perhaps because of Obama's youth, intellect, and eloquence, that he can not maintain even a facade of civility. And second, McCain was born in the 1930s so he probably learned to use the phrase during his formative years, and flashed back to it absentmindedly during a particularly stressful exchange during the debate.
http://www.youtube.com/watch?v=FcUi6UEQh00&feature=related