Conventional wisdom dictates against quoting Joseph Stalin during a Republican presidential primary debate, but if you must, it is best to use a real quotation.

Neurosurgeon Ben Carson failed to heed that dictum that Saturday night when he cited a quote incorrectly attributed to Joseph Stalin, the former Soviet premier.

"Joseph Stalin said, 'If you want to bring America down, you have to undermine three things: Our spiritual life, our patriotism, and our morality,'" Carson said during his closing statement at Saturday's Republican debate on CBS.

The problem is, the former Soviet leader never said that, or anything much like it.

Carson's mistaken use of the line likely originated from a Internet meme, called, "Stalin on America's Freedoms and Greatness," that circulates in conservative parts of the Web.

"America is a like a healthy body and its resistance is threefold: its patriotism, its morality, and its spiritual life. If we can undermine these three areas, America will collapse from within," the meme reads, attributing the analogy to Stalin.

But debate watchers immediately noted that the quotation is among hundreds of lines falsely attributed online and elsewhere to famous figures. Even a brain surgeon, it seems, can be fooled by bad online information.