Why would this have an impact on the election? It's not as if Romneys going to agree with it regardless of what he thinks.
It's not like Romney had African American vote to begin with.
Who knows how things will turn out? I don't. But sometimes little things like that can turn an election because they can cause one side to have to play defense instead of going on offense. They also energize the other side.
Romney is not yet doing as well among white voters as McCain did. It's not just black voters he has to worry about. There are plenty of white voters who will be turned off by such things. There are many independent or moderately conservative white voters that lean Republican or are looking for reasons to vote Republican.
When party leaders continually give indications that they think the wrong side won the Civil War or rape is no big deal or anyone who is darker than Desi Arnaz ought to be stopped and asked to prove citizenship the party risks losing some of those predominantly white swing voters.
Right now the election looks very close and neither side wants its nuts saying stupid things.