I used to hate accusations of racism at every turn. It made me think that the left always had to play the victim to score political points. Then I moved to the midwest. Let me assure you, there are some racist motherfuckers out here. It's nothing like what I experienced on the west coast.
Politicians all use pollsters, not only to see what kind of support they have, but also to see how to best express themselves. You can ask someone the same question in two different ways and get wildly different reactions from them. So I imagine that when these pollsters talk to some of these backward racist pieces of crap out here, they probably do respond favorably to language that implies that minorities are inferior.
When I hear a politician make a vague slightly racist sounding statement, I don't assume that he's a racist. I assume he's a bourgeois rich asshole who has no idea how to get regular people to like him. I think he took his pollsters' advise on how to word something and is genuinely shocked to find that some found it racist.
In short, I think it has more to do with a politicians' audience than it does with what's going on in their heads.