Technically, artbrooks, you're correct, but statistical "meaningfulness" isn't the same as sociopolitical (and psychological) "meaningfulness." I believe that including the troubling 31% with the scary 17% reveals the "abysmal ignorance" yet more clearly.

At best, about one-third are clueless about an issue that's a lot less complicated and subject to clever misrepresentation than, say, global warming.

Those who think they "know" he's a Muslim may be afflicted more by hatred, paranoia, and gullible acceptance than by simple ignorance. If so, that would make the overall voter profile even more dismaying.