EDIT: See updates below. The actual thing Romney said was probably slightly different, and it is not clear that it ought to be considered a “slogan” really.
There is occasional discussion of the observation that one of Romney’s speeches contained a phrase, “keep America American”, which was also a slogan used by the KKK in the 1920s, and even the 1950s. Trueish, though not precisely correct. Back in December of last year, MSNBC apologized for reporting on this in a way that implied that the resemblence was intentional. Furthermore, it’s since been pointed out that Romney actually said something slightly different. (“Keep America America”, not “Keep America American”.) And certainly, there’s not much evidence to suggest that it’s intentional. (I don’t really have any evidence that it isn’t, but there’s no basis for assuming it is.)
But the thing is, while it’s certainly ridiculous to imply that Romney is intentionally calling to mind the KKK’s slogan… That doesn’t mean that it’s really just a “coincidence”. The point of the slogan is to appeal to a particular emotional response; it ties in strongly with the spirit of Romney’s “joke” about how no one’s asked to see his birth certificate. Time and time again, Romney just happens to make remarks that would remind all the racists: Romney’s white. The other guy’s not. Romney talks about keeping immigrants out. It’s an appeal to the notion that if we don’t do something, our nation will be overrun with foreigners, with people who aren’t like us.
The thing about that slogan isn’t that the KKK had it first. It’s that it is a slogan which is by nature strongly appealing to the sorts of people the KKK wanted to reach. It is a slogan about drawing a clear line between us and them. And “us,” it turns out, means “white”.
Romney didn’t use “a KKK slogan”. Romney used a phrase which was designed to evoke a particular set of emotional responses. The KKK used a slogan which was designed to evoke a particular set of emotional responses. Since they were both going for the same set of emotional responses, they both came up with similar wording.
This isn’t something that ought to be some huge scandal because it proves Romney’s a secret Klansman. At the same time, the mere fact that he didn’t get the phrase from them doesn’t mean that it’s not a very disturbing phrase.