It's basically the same meme as the "he's such a great orator that he must be dumb" one that Synth Patel brought up a while ago.
Who says that though?
To clarify, "is dumb" in my post stands in for "has no substance" and its variants. Sorry for the phrasing.
It's a popular meme and not a stock one used to attack liberals (unlike the elitist and traitor labels which have long precedents). Seems to me that it has a lot to do with Obama's success and his presentation.
People see a relatively good looking young man performing on stage in front of thousands of adoring young admirers and they naturally go to their archetype of an entertainer. From there it's intuitive to dismiss him as empty and his supporters as faddists and naifs.
Most or all of the people who say this stuff about Obama are not terribly informed about policy themselves so I figure they're going off a gut feeling.
