There are some ideas so wrong that only a very intelligent person could believe in them.- George Orwell, born on this date in 1903
There is, however, the widely promoted idea of "change you can believe in," which subverts Orwell's notion of belief by only very intelligent people; the majority of the American voters (though not the majority of the population, which is a very different thing) somehow could not be accused of being "very intelligent," yet the wrongfulness of the idea was embraced with idiotic belief. Perhaps Orwell would be amused and forced to revise his opinion.(Word verification: bonic. There is an ironic pun embedded there, but perhaps I am overstating the obvious.)
Well, R.T., as Mencken once observed, no man ever lost money by underestimating the intelligence of the American people. On the other hand, an awful lot of putatively intelligent people -- and not just on these shores -- bought the hopey-changey business. As for a notion that fits what Orwell said perfectly, how about the meme. Not one shred of evidence that memes are real, but some very intelligent people talk about them all the time.
Ah, you have shifted from Orwell to Mencken to something else. Well, let me go a step further. "Some very intelligent people talk about" memes even though there is "not one shred of evidence that memes are real." Hmmm. Let us set aside the problematic word "real," for the time being, and consider instead, for a moment, the ostensible author of all the post-modern interest in memes: Richard Dawkins? Highly intelligent? Perhaps. And that, of course, tends to further the argument that intelligence should not be confused with wisdom. And so, by circuitous logic, we are back to Orwell's notion that "some ideas are so wrong that only a very intelligent [though bone-headed and misguided] person could believe in them."