I remember Hillary Clinton saying something similar, back in February?, along the lines as B.O. not being electable.
If not Hillary personally, certainly her surrogates. But one thing I do remember her saying specifically—and commented on at the time—was how she was so much more preferable than Obama because she’s been thoroughly “vetted.” She said this more than once, and so did her surrogates. So this was a decided-upon meme. It seemed an odd, inside-baseball kind of thing to say that smacked of morse code aimed at reporters, not primary voters, who don’t use those kinds of terms. I read it as a invitation to do some digging. IMHO.