If the X in the sentence "X made a comment about President Obama selling watermelons this weekend" were a prominent person of the Republican persuasion, X would probably be in the center of a media firestorm right now. In non-hypothetical terms, X is Dan Rather, who said this over the weekend on The Chris Matthews Show:
And the Republicans will make a case and a lot of independents will buy this argument. "Listen he just hasn't been, look at the health care bill. It was his number one priority. It took him forever to get it through and he had to compromise it to death." And a version of, "Listen he's a nice person, he's very articulate" this is what's been used against him, "but he couldn't sell watermelons if it, you gave him the state troopers to flag down the traffic."
It would probably be reading too much into the statement if we assumed that, because Rather was momentarily taking on the role of a Republican, maybe he just assumed the GOP would decide to infuse their messaging with some racist undertones. More likely is that, for one reason or another, watermelons were the first thing that popped into Rather's head when he was coming up with something for Obama to sell in that little analogy of his. Maybe it's because Rather harbors some subconscious racial stereotypes, or because, in his mind, a watermelon is a good example of something that's very easy to sell, especially when state troopers are controlling traffic (?). Either way, a good rule of thumb is to just never mention Obama and watermelons in the same sentence.