The word 'Nigger' has had derogatory implications for years, it used to be a demeaning term for slaves which was used in much the same context as a pet like a Cat or a Dog, but with considerably less affection attached. Yes, it was also a colour, (there used to be an oil paint that used that word to describe itself) but it's cart-before-horse, the word denoting the colour came from the perceived colour of the people themselves.
Like many words, it also depends on the intention of its use, and Fag is an excellent example, because in the UK "I'm going to smoke a Fag" is something completely different to the US. But, like many other racial 'nicknames' that have obtained negative connections, words such as that are an extremely loaded subject.
With regards to the OT, I actually think he said 'Governmentnik' and then '-er' as a natural hesitation, just at precisely the wrong moment (much like someone who is vehemently anti war is called a Peacenik, maybe he was trying to say that Obama was addicted to large Government), which transformed the word. That said people will read it as they see fit, and I won't cry any tears if it has a negative impact on his chances.
